Device-to-device (D2D) pre-emption and access control

ABSTRACT

Systems, methods, and instrumentalities are disclosed to determine access control and channel and signaling priority. A wireless transmit/receive unit (WTRU) may comprise a processor configured, at least in part, to determine device-to-device (D2D) data to be transmitted. The WTRU may determine if the D2D data may be transmitted. The WTRU may determine available scheduling assignment (SA) resources used for priority based D2D data signals. The WTRU may select one or more available SA resources used for priority based D2D data signals. The WTRU may transmit the D2D data, wherein the D2D data may be transmitted on the selected SA resources.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.16/764,258, filed May 14, 2020, which is the U.S. National Stage entry,under 35 U.S.C. § 371, of International Application No.PCT/US2018/061077 filed Nov. 14, 2018, which claims the benefit of U.S.Provisional Application No. 62/720,614, filed Aug. 21, 2018, and U.S.Provisional Application No. 62/586,642, filed Nov. 15, 2017, thecontents of which are hereby incorporated by reference herein.

BACKGROUND

Device-to-device (D2D) communications may be utilized for variouspurposes, such as public safety communications. D2D communications maybe associated with standardized technologies, such as LTE, IEEE, etc. InLTE systems, access control and/or priority handling may be used toarbitrate access to and/or usage of wireless resources by terminals.

SUMMARY

Systems, methods, and instrumentalities are disclosed to determineaccess control and channel and signaling priority. A wirelesstransmit/receive unit (WTRU) may comprise a processor configured, atleast in part, to determine device-to-device (D2D) data to betransmitted. The WTRU may determine if the D2D data may be transmitted.The WTRU may determine available scheduling assignment (SA) resourcesused for priority based D2D data signals. The WTRU may select one ormore available SA resources used for priority based D2D data signals.The WTRU may transmit the D2D data, wherein the D2D data may betransmitted on the selected SA resources.

The WTRU may be configured to select the available SA resources from apreconfigured set of SA resources. The WTRU may be configured to receiveconfiguration signaling and/or determine the available SA resources fromthe received configuration signaling.

Embodiments contemplate priority reception and/or transmission for D2Drelays, for example. Embodiments contemplate signaling for usage of(e.g., guaranteed) segregated resources.

A wireless transmit/receive unit (WTRU) may comprise a receiver. Thereceiver may be configured to receive an allocation of one or more radioresources for one or more scheduling assignments (SA). The WTRU maycomprise a processor. The processor may be configured to determine afirst frequency domain SA (FD SA) pool. The first FD SA pool may includeone or more SA allocated for at least one of a first prioritydevice-to-device (D2D) transmission. The processor may be configured todetermine a second FD SA pool. The second FD SA pool may include one ormore SA allocated for at least one of a second priority D2Dtransmission. The WTRU may comprise a transmitter. The transmitter maybe configured to send the at least one first priority D2D transmissionusing at least one radio resource for the one or more SA from the firstFD SA pool. The transmitter may be configured to send the at least onesecond priority D2D transmission using at least one radio resource forthe one or more SA from the second FD SA pool.

A wireless transmit/receive unit (WTRU) may be capable ofdevice-to-device (D2D) communication. The WTRU may comprise a receiver.The receiver may be configured to receive at least one of: a first D2Dchannel or a first D2D signal. The WTRU may comprise a processor. Theprocessor may be configured to determine if at least one of: a secondD2D channel or a second D2D signal is to be transmitted while the atleast one of: the first D2D channel or the first D2D signal is beingreceived. The processor may be configured to determine a relativepriority between the at least one of: the first D2D channel or the firstD2D signal, and the at least one of: the second D2D channel or thesecond D2D signal upon determining that the at least one of: a secondD2D channel or a second D2D signal is to be transmitted while the atleast one of: the first D2D channel or the first D2D signal is beingreceived. The processor may be configured to determine a number of D2Dsubframes to be used for receiving which of the first D2D channel or thefirst D2D signal, or the second D2D channel or the second D2D signal hasthe higher relative priority.

A wireless transmit/receive unit (WTRU) may be capable ofdevice-to-device (D2D) communication. The WTRU may comprise a processor.The processor may be configured to determine to transmit a pre-emptionindication. The processor may be configured to determine to transmit thepre-emption indication via a scheduling assignment (SA). The WTRU maycomprise a transmitter. The transmitter may be configured to send the SAas part of a control signal to another WTRU capable of D2Dcommunication.

A wireless transmit/receive unit (WTRU) may comprise a receiver. Thereceiver may be configured to receive an allocation of one or more radioresources for one or more scheduling assignments (SA). The WTRU maycomprise a processor. The processor may be configured to determine afirst SA pool. The first SA pool may include one or more SA allocatedfor at least one of a first priority device-to-device (D2D)transmission. The processor may be configured to determine a second SApool. The second SA pool may include one or more SA allocated for atleast one of a second priority D2D transmission. The processor may beconfigured to compare a number of first priority scheduling occurrencesassociated with one or more resources for the one or more SA of thefirst SA pool to a threshold. The WTRU may comprise a transmitter. Thetransmitter may be configured to send the at least one first priorityD2D transmission using at least one radio resource for the one or moreSA from the first SA pool upon the number equaling or exceeding thethreshold.

BRIEF DESCRIPTION OF THE DRAWINGS

A more detailed understanding may be had from the following description,given by way of example in conjunction with the accompanying drawings.

FIG. 1A is a system diagram of an example communications system in whichone or more disclosed embodiments may be implemented.

FIG. 1B is a system diagram of an example wireless transmit/receive unit(WTRU) that may be used within the communications system illustrated inFIG. 1A.

FIG. 10 is a system diagram of an example radio access network and anexample core network that may be used within the communications systemillustrated in FIG. 1A.

FIG. 1D is a system diagram of another example radio access network andan example core network that may be used within the communicationssystem illustrated in FIG. 1A.

FIG. 1E is a system diagram of another example radio access network andan example core network that may be used within the communicationssystem illustrated in FIG. 1A.

FIG. 2 is an example of priority based access through TDM in the SA andthe D2D data subframes.

FIG. 3 is an example of priority based access for D2D communicationsthrough TDM of SA in shared D2D data subframes.

FIG. 4 is an example of priority based access for D2D communicationsthrough FDM in the SA and the D2D data subframes.

FIG. 5 is an example of priority based access for D2D communicationsthrough FDM of SA in shared D2D data subframes.

FIG. 6 is an example of priority based access through different resourceallocation densities for D2D subframe pools (for example, TDM).

FIG. 7 is an example of priority based access through different resourceallocation densities (for example, Transmission Patterns).

FIG. 8 is an example of priority based access for D2D data usingpersistence parameters (for example, SA).

FIG. 9 is an example of prioritized reception of a high-priority channelby D2D terminal with FDD half-duplex operation.

FIG. 10 is an example of multiple concurrently received D2D channels(for example, voice).

FIG. 11 is an example of multiple concurrently D2D channels to betransmitted (for example, voice and data).

DETAILED DESCRIPTION

A detailed description of illustrative embodiments will now be describedwith reference to the various Figures. Although this descriptionprovides a detailed example of possible implementations, it should benoted that the details are intended to be examples and in no way limitthe scope of the application. As used herein, the articles “a” and “an”,absent further qualification or characterization, may be understood tomean “one or more” or “at least one”, for example.

FIG. 1A is a diagram of an example communications system 100 in whichone or more disclosed embodiments may be implemented. The communicationssystem 100 may be a multiple access system that provides content, suchas voice, data, video, messaging, broadcast, etc., to multiple wirelessusers. The communications system 100 may enable multiple wireless usersto access such content through the sharing of system resources,including wireless bandwidth. For example, the communications systems100 may employ one or more channel access methods, such as code divisionmultiple access (CDMA), time division multiple access (TDMA), frequencydivision multiple access (FDMA), orthogonal FDMA (OFDMA), single-carrierFDMA (SC-FDMA), and the like.

As shown in FIG. 1A, the communications system 100 may include wirelesstransmit/receive units (WTRUs) 102 a, 102 b, 102 c, and/or 102 d (whichgenerally or collectively may be referred to as WTRU 102), a radioaccess network (RAN) 103/104/105, a core network 106/107/109, a publicswitched telephone network (PSTN) 108, the Internet 110, and othernetworks 112, though it will be appreciated that the disclosedembodiments contemplate any number of WTRUs, base stations, networks,and/or network elements. Each of the WTRUs 102 a, 102 b, 102 c, 102 dmay be any type of device configured to operate and/or communicate in awireless environment. By way of example, the WTRUs 102 a, 102 b, 102 c,102 d may be configured to transmit and/or receive wireless signals andmay include user equipment (WTRU), a mobile station, a fixed or mobilesubscriber unit, a pager, a cellular telephone, a personal digitalassistant (PDA), a smartphone, a laptop, a netbook, a personal computer,a wireless sensor, consumer electronics, and the like.

The communications systems 100 may also include a base station 114 a anda base station 114 b. Each of the base stations 114 a, 114 b may be anytype of device configured to wirelessly interface with at least one ofthe WTRUs 102 a, 102 b, 102 c, 102 d to facilitate access to one or morecommunication networks, such as the core network 106/107/109, theInternet 110, and/or the networks 112. By way of example, the basestations 114 a, 114 b may be a base transceiver station (BTS), a Node-B,an eNode B, a Home Node B, a Home eNode B, a site controller, an accesspoint (AP), a wireless router, and the like. While the base stations 114a, 114 b are each depicted as a single element, it will be appreciatedthat the base stations 114 a, 114 b may include any number ofinterconnected base stations and/or network elements.

The base station 114 a may be part of the RAN 103/104/105, which mayalso include other base stations and/or network elements (not shown),such as a base station controller (BSC), a radio network controller(RNC), relay nodes, etc. The base station 114 a and/or the base station114 b may be configured to transmit and/or receive wireless signalswithin a particular geographic region, which may be referred to as acell (not shown). The cell may further be divided into cell sectors. Forexample, the cell associated with the base station 114 a may be dividedinto three sectors. Thus, in one embodiment, the base station 114 a mayinclude three transceivers, e.g., one for each sector of the cell. Inanother embodiment, the base station 114 a may employ multiple-inputmultiple output (MIMO) technology and, therefore, may utilize multipletransceivers for each sector of the cell.

The base stations 114 a, 114 b may communicate with one or more of theWTRUs 102 a, 102 b, 102 c, 102 d over an air interface 115/116/117,which may be any suitable wireless communication link (e.g., radiofrequency (RF), microwave, infrared (IR), ultraviolet (UV), visiblelight, etc.). The air interface 115/116/117 may be established using anysuitable radio access technology (RAT).

More specifically, as noted above, the communications system 100 may bea multiple access system and may employ one or more channel accessschemes, such as CDMA, TDMA, FDMA, OFDMA, SC-FDMA, and the like. Forexample, the base station 114 a in the RAN 103/104/105 and the WTRUs 102a, 102 b, 102 c may implement a radio technology such as UniversalMobile Telecommunications System (UMTS) Terrestrial Radio Access (UTRA),which may establish the air interface 115/116/117 using wideband CDMA(WCDMA). WCDMA may include communication protocols such as High-SpeedPacket Access (HSPA) and/or Evolved HSPA (HSPA+). HSPA may includeHigh-Speed Downlink Packet Access (HSDPA) and/or High-Speed UplinkPacket Access (HSUPA).

In another embodiment, the base station 114 a and the WTRUs 102 a, 102b, 102 c may implement a radio technology such as Evolved UMTSTerrestrial Radio Access (E-UTRA), which may establish the air interface115/116/117 using Long Term Evolution (LTE) and/or LTE-Advanced (LTE-A).

In other embodiments, the base station 114 a and the WTRUs 102 a, 102 b,102 c may implement radio technologies such as IEEE 802.16 (e.g.,Worldwide Interoperability for Microwave Access (WiMAX)), CDMA2000,CDMA2000 1×, CDMA2000 EV-DO, Interim Standard 2000 (IS-2000), InterimStandard 95 (IS-95), Interim Standard 856 (IS-856), Global System forMobile communications (GSM), Enhanced Data rates for GSM Evolution(EDGE), GSM EDGE (GERAN), and the like.

The base station 114 b in FIG. 1A may be a wireless router, Home Node B,Home eNode B, or access point, for example, and may utilize any suitableRAT for facilitating wireless connectivity in a localized area, such asa place of business, a home, a vehicle, a campus, and the like. In oneembodiment, the base station 114 b and the WTRUs 102 c, 102 d mayimplement a radio technology such as IEEE 802.11 to establish a wirelesslocal area network (WLAN). In another embodiment, the base station 114 band the WTRUs 102 c, 102 d may implement a radio technology such as IEEE802.15 to establish a wireless personal area network (WPAN). In yetanother embodiment, the base station 114 b and the WTRUs 102 c, 102 dmay utilize a cellular-based RAT (e.g., WCDMA, CDMA2000, GSM, LTE,LTE-A, etc.) to establish a picocell or femtocell. As shown in FIG. 1A,the base station 114 b may have a direct connection to the Internet 110.Thus, the base station 114 b may not be required to access the Internet110 via the core network 106/107/109.

The RAN 103/104/105 may be in communication with the core network106/107/109, which may be any type of network configured to providevoice, data, applications, and/or voice over internet protocol (VoIP)services to one or more of the WTRUs 102 a, 102 b, 102 c, 102 d. Forexample, the core network 106/107/109 may provide call control, billingservices, mobile location-based services, pre-paid calling, Internetconnectivity, video distribution, etc., and/or perform high-levelsecurity functions, such as user authentication. Although not shown inFIG. 1A, it will be appreciated that the RAN 103/104/105 and/or the corenetwork 106/107/109 may be in direct or indirect communication withother RANs that employ the same RAT as the RAN 103/104/105 or adifferent RAT. For example, in addition to being connected to the RAN103/104/105, which may be utilizing an E-UTRA radio technology, the corenetwork 106/107/109 may also be in communication with another RAN (notshown) employing a GSM radio technology.

The core network 106/107/109 may also serve as a gateway for the WTRUs102 a, 102 b, 102 c, 102 d to access the PSTN 108, the Internet 110,and/or other networks 112. The PSTN 108 may include circuit-switchedtelephone networks that provide plain old telephone service (POTS). TheInternet 110 may include a global system of interconnected computernetworks and devices that use common communication protocols, such asthe transmission control protocol (TCP), user datagram protocol (UDP)and the internet protocol (IP) in the TCP/IP internet protocol suite.The networks 112 may include wired or wireless communications networksowned and/or operated by other service providers. For example, thenetworks 112 may include another core network connected to one or moreRANs, which may employ the same RAT as the RAN 103/104/105 or adifferent RAT.

Some or all of the WTRUs 102 a, 102 b, 102 c, 102 d in thecommunications system 100 may include multi-mode capabilities, e.g., theWTRUs 102 a, 102 b, 102 c, 102 d may include multiple transceivers forcommunicating with different wireless networks over different wirelesslinks. For example, the WTRU 102 c shown in FIG. 1A may be configured tocommunicate with the base station 114 a, which may employ acellular-based radio technology, and with the base station 114 b, whichmay employ an IEEE 802 radio technology.

FIG. 1B is a system diagram of an example WTRU 102. As shown in FIG. 1B,the WTRU 102 may include a processor 118, a transceiver 120, atransmit/receive element 122, a speaker/microphone 124, a keypad 126, adisplay/touchpad 128, non-removable memory 130, removable memory 132, apower source 134, a global positioning system (GPS) chipset 136, andother peripherals 138. It will be appreciated that the WTRU 102 mayinclude any sub-combination of the foregoing elements while remainingconsistent with an embodiment. Also, embodiments contemplate that thebase stations 114 a and 114 b, and/or the nodes that base stations 114 aand 114 b may represent, such as but not limited to transceiver station(BTS), a Node-B, a site controller, an access point (AP), a home node-B,an evolved home node-B (eNodeB), a home evolved node-B (HeNB), a homeevolved node-B gateway, and proxy nodes, among others, may include someor all of the elements depicted in FIG. 1B and described herein.

The processor 118 may be a general purpose processor, a special purposeprocessor, a conventional processor, a digital signal processor (DSP), aplurality of microprocessors, one or more microprocessors in associationwith a DSP core, a controller, a microcontroller, Application SpecificIntegrated Circuits (ASICs), Field Programmable Gate Array (FPGAs)circuits, any other type of integrated circuit (IC), a state machine,and the like. The processor 118 may perform signal coding, dataprocessing, power control, input/output processing, and/or any otherfunctionality that enables the WTRU 102 to operate in a wirelessenvironment. The processor 118 may be coupled to the transceiver 120,which may be coupled to the transmit/receive element 122. While FIG. 1Bdepicts the processor 118 and the transceiver 120 as separatecomponents, it will be appreciated that the processor 118 and thetransceiver 120 may be integrated together in an electronic package orchip.

The transmit/receive element 122 may be configured to transmit signalsto, or receive signals from, a base station (e.g., the base station 114a) over the air interface 115/116/117. For example, in one embodiment,the transmit/receive element 122 may be an antenna configured totransmit and/or receive RF signals. In another embodiment, thetransmit/receive element 122 may be an emitter/detector configured totransmit and/or receive IR, UV, or visible light signals, for example.In yet another embodiment, the transmit/receive element 122 may beconfigured to transmit and receive both RF and light signals. It will beappreciated that the transmit/receive element 122 may be configured totransmit and/or receive any combination of wireless signals.

In addition, although the transmit/receive element 122 is depicted inFIG. 1B as a single element, the WTRU 102 may include any number oftransmit/receive elements 122. More specifically, the WTRU 102 mayemploy MIMO technology. Thus, in one embodiment, the WTRU 102 mayinclude two or more transmit/receive elements 122 (e.g., multipleantennas) for transmitting and receiving wireless signals over the airinterface 115/116/117.

The transceiver 120 may be configured to modulate the signals that areto be transmitted by the transmit/receive element 122 and to demodulatethe signals that are received by the transmit/receive element 122. Asnoted above, the WTRU 102 may have multi-mode capabilities. Thus, thetransceiver 120 may include multiple transceivers for enabling the WTRU102 to communicate via multiple RATs, such as UTRA and IEEE 802.11, forexample.

The processor 118 of the WTRU 102 may be coupled to, and may receiveuser input data from, the speaker/microphone 124, the keypad 126, and/orthe display/touchpad 128 (e.g., a liquid crystal display (LCD) displayunit or organic light-emitting diode (OLED) display unit). The processor118 may also output user data to the speaker/microphone 124, the keypad126, and/or the display/touchpad 128. In addition, the processor 118 mayaccess information from, and store data in, any type of suitable memory,such as the non-removable memory 130 and/or the removable memory 132.The non-removable memory 130 may include random-access memory (RAM),read-only memory (ROM), a hard disk, or any other type of memory storagedevice. The removable memory 132 may include a subscriber identitymodule (SIM) card, a memory stick, a secure digital (SD) memory card,and the like. In other embodiments, the processor 118 may accessinformation from, and store data in, memory that is not physicallylocated on the WTRU 102, such as on a server or a home computer (notshown).

The processor 118 may receive power from the power source 134, and maybe configured to distribute and/or control the power to the othercomponents in the WTRU 102. The power source 134 may be any suitabledevice for powering the WTRU 102. For example, the power source 134 mayinclude one or more dry cell batteries (e.g., nickel-cadmium (NiCd),nickel-zinc (NiZn), nickel metal hydride (NiMH), lithium-ion (Li-ion),etc.), solar cells, fuel cells, and the like.

The processor 118 may also be coupled to the GPS chipset 136, which maybe configured to provide location information (e.g., longitude andlatitude) regarding the current location of the WTRU 102. In additionto, or in lieu of, the information from the GPS chipset 136, the WTRU102 may receive location information over the air interface 115/116/117from a base station (e.g., base stations 114 a, 114 b) and/or determineits location based on the timing of the signals being received from twoor more nearby base stations. It will be appreciated that the WTRU 102may acquire location information by way of any suitablelocation-determination method while remaining consistent with anembodiment.

The processor 118 may further be coupled to other peripherals 138, whichmay include one or more software and/or hardware modules that provideadditional features, functionality and/or wired or wirelessconnectivity. For example, the peripherals 138 may include anaccelerometer, an e-compass, a satellite transceiver, a digital camera(for photographs or video), a universal serial bus (USB) port, avibration device, a television transceiver, a hands free headset, aBluetooth® module, a frequency modulated (FM) radio unit, a digitalmusic player, a media player, a video game player module, an Internetbrowser, and the like.

FIG. 10 is a system diagram of the RAN 103 and the core network 106according to an embodiment. As noted above, the RAN 103 may employ aUTRA radio technology to communicate with the WTRUs 102 a, 102 b, 102 cover the air interface 115. The RAN 103 may also be in communicationwith the core network 106. As shown in FIG. 10 , the RAN 103 may includeNode-Bs 140 a, 140 b, 140 c, which may each include one or moretransceivers for communicating with the WTRUs 102 a, 102 b, 102 c overthe air interface 115. The Node-Bs 140 a, 140 b, 140 c may each beassociated with a particular cell (not shown) within the RAN 103. TheRAN 103 may also include RNCs 142 a, 142 b. It will be appreciated thatthe RAN 103 may include any number of Node-Bs and RNCs while remainingconsistent with an embodiment.

As shown in FIG. 10 , the Node-Bs 140 a, 140 b may be in communicationwith the RNC 142 a. Additionally, the Node-B 140 c may be incommunication with the RNC 142 b. The Node-Bs 140 a, 140 b, 140 c maycommunicate with the respective RNCs 142 a, 142 b via an Iub interface.The RNCs 142 a, 142 b may be in communication with one another via anIur interface. Each of the RNCs 142 a, 142 b may be configured tocontrol the respective Node-Bs 140 a, 140 b, 140 c to which it isconnected. In addition, each of the RNCs 142 a, 142 b may be configuredto carry out or support other functionality, such as outer loop powercontrol, load control, admission control, packet scheduling, handovercontrol, macrodiversity, security functions, data encryption, and thelike.

The core network 106 shown in FIG. 10 may include a media gateway (MGVV)144, a mobile switching center (MSC) 146, a serving GPRS support node(SGSN) 148, and/or a gateway GPRS support node (GGSN) 150. While each ofthe foregoing elements are depicted as part of the core network 106, itwill be appreciated that any one of these elements may be owned and/oroperated by an entity other than the core network operator.

The RNC 142 a in the RAN 103 may be connected to the MSC 146 in the corenetwork 106 via an IuCS interface. The MSC 146 may be connected to theMGW 144. The MSC 146 and the MGW 144 may provide the WTRUs 102 a, 102 b,102 c with access to circuit-switched networks, such as the PSTN 108, tofacilitate communications between the WTRUs 102 a, 102 b, 102 c andtraditional land-line communications devices.

The RNC 142 a in the RAN 103 may also be connected to the SGSN 148 inthe core network 106 via an IuPS interface. The SGSN 148 may beconnected to the GGSN 150. The SGSN 148 and the GGSN 150 may provide theWTRUs 102 a, 102 b, 102 c with access to packet-switched networks, suchas the Internet 110, to facilitate communications between and the WTRUs102 a, 102 b, 102 c and IP-enabled devices.

As noted above, the core network 106 may also be connected to thenetworks 112, which may include other wired or wireless networks thatare owned and/or operated by other service providers.

FIG. 1D is a system diagram of the RAN 104 and the core network 107according to an embodiment. As noted above, the RAN 104 may employ anE-UTRA radio technology to communicate with the WTRUs 102 a, 102 b, 102c over the air interface 116. The RAN 104 may also be in communicationwith the core network 107.

The RAN 104 may include eNode-Bs 160 a, 160 b, 160 c, though it will beappreciated that the RAN 104 may include any number of eNode-Bs whileremaining consistent with an embodiment. The eNode-Bs 160 a, 160 b, 160c may each include one or more transceivers for communicating with theWTRUs 102 a, 102 b, 102 c over the air interface 116. In one embodiment,the eNode-Bs 160 a, 160 b, 160 c may implement MIMO technology. Thus,the eNode-B 160 a, for example, may use multiple antennas to transmitwireless signals to, and receive wireless signals from, the WTRU 102 a.

Each of the eNode-Bs 160 a, 160 b, 160 c may be associated with aparticular cell (not shown) and may be configured to handle radioresource management decisions, handover decisions, scheduling of usersin the uplink and/or downlink, and the like. As shown in FIG. 1D, theeNode-Bs 160 a, 160 b, 160 c may communicate with one another over an X2interface.

The core network 107 shown in FIG. 1D may include a mobility managementgateway (MME) 162, a serving gateway 164, and a packet data network(PDN) gateway 166. While each of the foregoing elements are depicted aspart of the core network 107, it will be appreciated that any one ofthese elements may be owned and/or operated by an entity other than thecore network operator.

The MME 162 may be connected to each of the eNode-Bs 160 a, 160 b, 160 cin the RAN 104 via an S1 interface and may serve as a control node. Forexample, the MME 162 may be responsible for authenticating users of theWTRUs 102 a, 102 b, 102 c, bearer activation/deactivation, selecting aparticular serving gateway during an initial attach of the WTRUs 102 a,102 b, 102 c, and the like. The MME 162 may also provide a control planefunction for switching between the RAN 104 and other RANs (not shown)that employ other radio technologies, such as GSM or WCDMA.

The serving gateway 164 may be connected to each of the eNode-Bs 160 a,160 b, 160 c in the RAN 104 via the S1 interface. The serving gateway164 may generally route and forward user data packets to/from the WTRUs102 a, 102 b, 102 c. The serving gateway 164 may also perform otherfunctions, such as anchoring user planes during inter-eNode B handovers,triggering paging when downlink data is available for the WTRUs 102 a,102 b, 102 c, managing and storing contexts of the WTRUs 102 a, 102 b,102 c, and the like.

The serving gateway 164 may also be connected to the PDN gateway 166,which may provide the WTRUs 102 a, 102 b, 102 c with access topacket-switched networks, such as the Internet 110, to facilitatecommunications between the WTRUs 102 a, 102 b, 102 c and IP-enableddevices.

The core network 107 may facilitate communications with other networks.For example, the core network 107 may provide the WTRUs 102 a, 102 b,102 c with access to circuit-switched networks, such as the PSTN 108, tofacilitate communications between the WTRUs 102 a, 102 b, 102 c andtraditional land-line communications devices. For example, the corenetwork 107 may include, or may communicate with, an IP gateway (e.g.,an IP multimedia subsystem (IMS) server) that serves as an interfacebetween the core network 107 and the PSTN 108. In addition, the corenetwork 107 may provide the WTRUs 102 a, 102 b, 102 c with access to thenetworks 112, which may include other wired or wireless networks thatare owned and/or operated by other service providers.

FIG. 1E is a system diagram of the RAN 105 and the core network 109according to an embodiment. The RAN 105 may be an access service network(ASN) that employs IEEE 802.16 radio technology to communicate with theWTRUs 102 a, 102 b, 102 c over the air interface 117. As will be furtherdiscussed below, the communication links between the differentfunctional entities of the WTRUs 102 a, 102 b, 102 c, the RAN 105, andthe core network 109 may be defined as reference points.

As shown in FIG. 1E, the RAN 105 may include base stations 180 a, 180 b,180 c, and an ASN gateway 182, though it will be appreciated that theRAN 105 may include any number of base stations and ASN gateways whileremaining consistent with an embodiment. The base stations 180 a, 180 b,180 c may each be associated with a particular cell (not shown) in theRAN 105 and may each include one or more transceivers for communicatingwith the WTRUs 102 a, 102 b, 102 c over the air interface 117. In oneembodiment, the base stations 180 a, 180 b, 180 c may implement MIMOtechnology. Thus, the base station 180 a, for example, may use multipleantennas to transmit wireless signals to, and receive wireless signalsfrom, the WTRU 102 a. The base stations 180 a, 180 b, 180 c may alsoprovide mobility management functions, such as handoff triggering,tunnel establishment, radio resource management, traffic classification,quality of service (QoS) policy enforcement, and the like. The ASNgateway 182 may serve as a traffic aggregation point and may beresponsible for paging, caching of subscriber profiles, routing to thecore network 109, and the like.

The air interface 117 between the WTRUs 102 a, 102 b, 102 c and the RAN105 may be defined as an R1 reference point that implements the IEEE802.16 specification. In addition, each of the WTRUs 102 a, 102 b, 102 cmay establish a logical interface (not shown) with the core network 109.The logical interface between the WTRUs 102 a, 102 b, 102 c and the corenetwork 109 may be defined as an R2 reference point, which may be usedfor authentication, authorization, IP host configuration management,and/or mobility management.

The communication link between each of the base stations 180 a, 180 b,180 c may be defined as an R8 reference point that includes protocolsfor facilitating WTRU handovers and the transfer of data between basestations. The communication link between the base stations 180 a, 180 b,180 c and the ASN gateway 182 may be defined as an R6 reference point.The R6 reference point may include protocols for facilitating mobilitymanagement based on mobility events associated with each of the WTRUs102 a, 102 b, 102 c.

As shown in FIG. 1E, the RAN 105 may be connected to the core network109. The communication link between the RAN 105 and the core network 109may defined as an R3 reference point that includes protocols forfacilitating data transfer and mobility management capabilities, forexample. The core network 109 may include a mobile IP home agent(MIP-HA) 184, an authentication, authorization, accounting (AAA) server186, and a gateway 188. While each of the foregoing elements aredepicted as part of the core network 109, it will be appreciated thatany one of these elements may be owned and/or operated by an entityother than the core network operator.

The MIP-HA may be responsible for IP address management, and may enablethe WTRUs 102 a, 102 b, 102 c to roam between different ASNs and/ordifferent core networks. The MIP-HA 184 may provide the WTRUs 102 a, 102b, 102 c with access to packet-switched networks, such as the Internet110, to facilitate communications between the WTRUs 102 a, 102 b, 102 cand IP-enabled devices. The AAA server 186 may be responsible for userauthentication and for supporting user services. The gateway 188 mayfacilitate interworking with other networks. For example, the gateway188 may provide the WTRUs 102 a, 102 b, 102 c with access tocircuit-switched networks, such as the PSTN 108, to facilitatecommunications between the WTRUs 102 a, 102 b, 102 c and traditionalland-line communications devices. In addition, the gateway 188 mayprovide the WTRUs 102 a, 102 b, 102 c with access to the networks 112,which may include other wired or wireless networks that are owned and/oroperated by other service providers.

Although not shown in FIG. 1E, it will be appreciated that the RAN 105may be connected to other ASNs and the core network 109 may be connectedto other core networks. The communication link between the RAN 105 theother ASNs may be defined as an R4 reference point, which may includeprotocols for coordinating the mobility of the WTRUs 102 a, 102 b, 102 cbetween the RAN 105 and the other ASNs. The communication link betweenthe core network 109 and the other core networks may be defined as an R5reference, which may include protocols for facilitating interworkingbetween home core networks and visited core networks.

For 3GPP and/or LTE based radio access, support for D2D communicationsmay allow for cost-efficient and high-capability public safetycommunications using LTE technology. This may be motivated by the desireto harmonize the radio access technology across jurisdictions in orderto lower the CAPEX and OPEX of radio-access technology available for theuse of public safety (PS) type of applications. This may be motivated byLTE as a scalable wideband radio solution may allow for efficientmultiplexing of different services types like voice and video.

Since PS applications may utilize (e.g., typically require) radiocommunications in areas that might not be under radio coverage of an LTEnetwork, e.g. in tunnels, in deep basements, and/or followingcatastrophic system outages, there may be a usefulness to support D2Dcommunications for PS in absence of any operating network and/or priorto the arrival of AdHoc deployed radio infrastructure. Even whenoperating in presence of operating network infrastructure, PScommunications may utilize (e.g., typically require) higher reliabilitythan commercial services.

PS type of applications, e.g. between first responders, may includedirect push-to-talk speech services using multiple talk groups. PS typeof applications may include services such as video push or download, forexample, to make efficient use of the capabilities an LTE broadbandradio provides.

D2D communications may be available for PS type of applications and/orcommercial use cases, for example, perhaps when deployed. For example, acommercial use could be utility companies who often also require supportfor 2-way radio communications in areas not covered by networkinfrastructure. D2D services, such as discovery, are suitable signalingmechanisms to allow for proximity based services and/or traffic offloadusing LTE based radio access in commercial use cases.

Access control may be disclosed herein. Priority handling may bedisclosed herein.

In LTE systems, there may be access control and/or priority handlingmechanisms to arbitrate the access to and/or usage of wireless resourcesby terminals.

For example, system information broadcast (SIB) messages carried onbroadcast channel (BCH) may carry information for which access serviceclasses terminals attempting to connect to the cell are allowed, e.g.emergency only, maintenance only, and/or any type. Access control may bepossible, for example, once a terminal device is connected to an LTEcell. For example, if there are more terminals connected to a cell thancan be reliably supported, Access Stratum (AS) and/or Non-Access Stratum(NAS) connections from the network side may be terminated. Terminaldevices may be re-directed to channels and/or bands of another radioaccess technology like GSM or 3G HSPA in the operator's network.

Access control in existing LTE networks may exist in one or more (e.g.,many) forms. Access control in LTE networks may have in common thatterminal devices may be denied and/or limited, for example, in terms ofaccess to wireless resources by the network prior to a connectionattempt and/or while being connected to cell(s).

LTE systems may offer techniques for priority handling of concurrentlyrunning wireless services. Priority handling may be used to ensurehigher Quality of Service (QoS) data streams like conversational voice,video that may be served first, and/or with guaranteed bit rates orguaranteed latencies. Priority handling may be used to serve (e.g.,first serve) control signaling (e.g., useful/essential controlsignaling).

For example, in LTE systems, priority handling of data with multipleusers in the system may be possible by the base station (e.g., first)scheduling high-priority data with real-time QoS constraints in theDownlink (DL). Priority handling of data with multiple users in thesystem may be possible by the base station artificially reducing and/orthrottling service data rates for lower priority download type of data.Systems, such as when supporting emergency calls, may implement priorityhandling for E911 calls to guarantee successful call setup percentages(e.g., much) higher and/or occurrences of dropped calls (e.g., much)lower than typically guaranteed for regular voice calls. If a singleterminal device has multiple types of data to transmit concurrently,rules may specify to transmit higher priority data (e.g., first) when anUL transmission opportunity may have been granted. Lower priority datamay complete (e.g., later), for example, once packets allocated higherlogical channel priorities have completed their transmission.

Priority handling from the single user perspective and/or from thesystem perspective may be implemented in different forms in existing LTEsystems. These may have in common that higher priority data may betransmitted (e.g., first) perhaps if useful, and/or lower priority datamay be pre-empted from transmission if concurrent services have to besupported concurrently.

D2D communications may use LTE based radio access.

D2D communications using LTE based radio access may be designed tooperate in network-control mode and/or in WTRU autonomous mode.Network-control mode may be referred to as Mode 1 and WTRU autonomousmode may be referred to as Mode 2. Mode 1 (Network controlled) may bepossible (e.g., only possible) under certain conditions, for example, ifthe D2D terminal is in radio range of a LTE base station. The D2Dterminal may fall back to Mode 2 (WTRU autonomous) operation, forexample, if it cannot communicate with the LTE base station. In thiscase, it may mostly use channel access parameters pre-stored on theterminal itself.

For D2D communications using Mode 1, the LTE base station may reserve aselected set of UL subframes to allow for D2D transmissions. The LTEbase station may announce a set of UL subframes with associatedparameters in which D2D communications for neighbor cells and/or Mode 2terminals may be received. Less than all LTE system bandwidth (BW) maybe available for D2D transmissions in a subframe reserved for D2D.Perhaps when operating in Mode 1, for example, radio resources for D2Dcommunications may be granted to a D2D terminal by the serving cell. TheD2D grant from the network may be preceded by an UL transmission by theterminal on the cellular UL, for example, indicating to the base stationthe amount of available D2D data. The D2D grant received by the D2Dterminal from the LTE base station on the cellular DL may allow the D2Dterminal to use certain selected radio resources, for example some radioblocks (RBs) occurring in some subframes over a certain schedulingperiod.

The D2D terminal may transmit a Scheduling Assignment (SA) message in aset (e.g., first set) of one or more D2D subframe(s) and/or transmit theD2D data in a set (e.g., second set) of D2D subframes in a schedulingperiod. Scheduling assignments (e.g., and others) may contain anidentifier field, an MCS field, a resource indicator and TA field. D2Ddata packets (e.g., and others) may contain a MAC header with sourceand/or destination address. Multiple logical channels may be multiplexedand/or sent as part of a single transport block (TB) in a D2D subframeby a WTRU.

For D2D communications using Mode 2, the D2D terminals may select (e.g.,autonomously select) time/frequency radio resources. Channel accessparameters, such as the subframes for use with transmissions of SAcontrol messages and/or corresponding D2D data, scheduling periods ormonitoring subframes, may be pre-configured (e.g., typicallypre-configured) and/or stored on the D2D terminal. Mode 2 terminals mayfollow the same or similar transmission behavior as the Mode 1terminals, for example they may transmit SAs followed by D2D data inscheduling periods. The preceding UL traffic volume indication and/or DLD2D grant phase might not follow the same or similar transmissionbehavior as Mode 1 terminals.

For D2D communications in Mode 1 and Mode 2, D2D terminals may transmitauxiliary D2D signals, such as D2D synchronization signals and/orchannel messages to aid receivers in demodulating their transmissions.

D2D communications using LTE based radio access may carry voice channelsand/or data packets and/or data streams. D2D communications may includeD2D discovery service. D2D discovery (e.g., unlike voice channels) mayuse (e.g., only use) small packet transmissions that may fit in one, twoor few (e.g., at most) subframes. For example, these packets may containapplication data announcing availability of devices and/or SWapplications to participate in D2D data exchanges with terminals in thevicinity.

D2D discovery may or might not use the same or similar channel accessprotocol, such as may be used for D2D communications for voice and/orgeneric D2D data. For D2D discovery service, such as when in coverage ofan LTE base station, D2D discovery resources may be allocated (e.g.,separately allocated) from those used for D2D communications with voiceor generic D2D data. Radio resources for D2D discovery messages may beselected (e.g., autonomously) by D2D terminals from a set of resourcesthat may be reserved by the eNB and/or may be recurring (e.g.,periodically recurring) time-frequency radio resources in UL subframes(e.g., Type 1 discovery) and/or may be allocated (e.g., explicitlyallocated) by the LTE serving cell to the D2D terminals (e.g., Type 2discovery). The latter may be similar to D2D communications Mode 1.Transmissions of scheduling assignments might not be used whentransmitting D2D discovery messages. D2D terminals transmitting (e.g.,only transmitting) D2D discovery messages may be used to transmitauxiliary D2D synchronization signals to assist receivers.

Access control, priority handling and/or pre-emption mechanisms for D2Dcommunications using LTE based radio access comparable to conventionalLTE networks may be described herein.

D2D terminals, such as those for use with public safety applications,may be (e.g., inherently) designed to operate in absence of operatingLTE radio network infrastructure. This may imply that these devices maybe able to operate autonomously in terms of channel access and anyhandling of their D2D data transmissions. Unlike present LTE terminaldevices which may be mostly network-controlled through control signalingmessage exchanges with the LTE network, D2D terminal devices may store(e.g., typically store) some (e.g., most if not all) parameters that maydetermine their channel access and/or transmission behavior on the(U)SIM card and/or as part of the application software (SW).

Transmission procedures and/or channel access protocols for D2Dcommunications using LTE based radio access might not be designed toallow for random access to distinguish priorities for individual devicesand/or to allow for data transmission under consideration ofquality-of-service (QoS) for D2D data. A mechanism to deny, to limitand/or to restrict a particular device or user from access to D2D radioresources may exist.

Perhaps when in radio range of an LTE cell, among other scenarios, forexample, certain limitations onto allowable UL subframes that may bereserved for use by the D2D terminals in the vicinity may be imposed bythe LTE serving cell. Priority handling and channel access by differentusers or for different types of data transmitted from a given D2D usermight not be ensured deterministically. If (e.g., only if) D2D radioresources in the LTE serving cell are over-provisioned, successfulchannel access for high-priority terminals and successful transmissionof higher priority data may be ensured, for example, in the statisticalsense. In absence of operating LTE radio network infrastructure, theremay be less control over usage of the D2D radio resources.

A D2D terminal might not distinguish between different types of D2Ddata, for example, for radio resource allocation trade-offs.

D2D communications using LTE based radio access may allow for (e.g.,implicit) distinction of different types of D2D communications received,for example, when associating the encryption or message integrityprotection keys, and D2D service identifiers used for D2D SWapplications to secure D2D data payloads by transmitting devices. Whenkeys and identifiers are known, a transmitting D2D terminal or areceiving D2D terminal might not be able to distinguish higher priorityusers and/or higher priority type of D2D data, for example, until it mayhave (e.g., physically) demodulated and/or decoded any such D2Dtransmission. D2D devices might not take into account priority ofongoing and/or planned D2D communications, for example, when determiningtheir own transmission and/or reception behavior. A D2D terminal readyfor transmission might not refrain from channel access, for example,until it has (e.g., physically) demodulated one or more or all thechannels, such as in the presence of ongoing critical D2Dcommunications. D2D terminals might not be configured (e.g., neverconfigured) with the knowledge of one or more or all D2D identifiersand/or associated derived payload encryption and/or message integrityprotection keys that may be used in the vicinity by other D2D terminals.This means that one or more (e.g., most) D2D terminals may be obliviousto the kind and/or type of D2D data they attempt to decode anddistinguish based on the received D2D payload contents. The payloadmight not be decoded by such a D2D device in the absence of known keysand/or associated identifiers. Information about the carried D2D payloadmight not be derived.

Mechanisms for D2D communications using LTE radio access technology thatmay allow for priority based channel access, priority based handling ofD2D communications as a function of D2D terminal and/or type of D2D datato ensure service availability and QoS, and/or for pre-emption incritical circumstances may be described herein. Availability of prioritybased access and/or transmission mechanisms may enhance efficiency ofwireless transmissions, improve upon the usage of D2D radio resourcesand/or may improve upon channel and/or service availability for D2Dusers, for example, similar to conventional LTE networks.

The term D2D data may refer to D2D related communication between D2Dterminals. For example, without loss of generality, D2D data may includedata packets such as carrying voice or segments thereof, it may includeIP packets or segments thereof, such as used for file download orupload, streaming or bi-directional video, it may include D2D controlsignaling, or it may include D2D discovery or service or availabilitymessages, etc. The features disclosed herein may be described in thegeneral context of 3GPP D2D communications; the features may beapplicable to other features such as D2D discovery, for example.

D2D priority may be based on channel access. One or more (e.g.,different) SA and/or data pools may be used for priority-based access.Access mechanisms may be based on radio resource sets (e.g., segregatedradio resource sets).

Priority based access for D2D communications may use segregated radioresource sets in time-domain and/or in frequency-domain.

Segregated radio resource sets, in time and/or frequency domain for usewith prioritized D2D access may be realized on radio resources that maybe used for Scheduling Assignments (SA), D2D data, control or servicesignaling such as D2D discovery, for one of these D2D datasignals/channels, and/or for more than one of these D2D datasignals/channels.

FIG. 2 is an example diagram of priority based access through TDM in theSA and the D2D data subframes. Priority based access for D2Dcommunications may be realized through Time-Division-Multiplex (TDM) ofthe SA and/or the D2D data pools.

In the example of FIG. 2 , there are N=2 different SA pools and theirM=2 corresponding D2D data pools. The 2 different SA pools are definedover different and/or distinct subframe subsets in time-domain. In FIG.2 , there are L1=1 subframe for SAs per SA pool per scheduling period ofP=160 ms. The two D2D data pools may be defined over different and/ordistinct subframe subsets. In FIG. 2 , there are L2=18 availablesubframes per D2D data pool per scheduling period.

An SA pool (e.g., such as the first SA pool in FIG. 2 ) may carry SAsfor accompanying D2D data transmissions (e.g., high priority D2D datatransmissions) in the D2D data pool (e.g., first D2D data pool) over theduration of a scheduling period. High priority transmissions maycorrespond to a responder talk group (e.g., first responder talk group)and/or a high-priority voice channel. An SA pool (e.g., such as thesecond SA pool in FIG. 2 ) may carry SAs for corresponding lowerpriority D2D transmissions in a D2D data pool (e.g., second D2D datapool). A lower priority transmission may be a background file downloadand/or a non-time critical exchange of D2D service data.

High-priority D2D data transmissions may be done (e.g., only done) onradio resources used by the SA (e.g., first SA in FIG. 2 ) and/or thecorresponding D2D data pool (e.g., first D2D data pool in FIG. 2 ).Lower priority D2D data transmissions may occur (e.g., only occur) onthe radio resources used for the SA (e.g., second SA) and/or D2D datapool (e.g., second D2D data pool). An SA carried in a subframe of thehigh-priority (e.g., first) SA pool might not announce D2D data on radioresources for the low priority (e.g., second) D2D data pool. An SAcarried in a subframe of the low-priority (e.g., second) SA pool mightnot announce D2D data on radio resources for the high priority (e.g.,first) D2D data pool.

TDM in lower priority D2D transmissions might not be able to occur onthe higher priority SA/data pools, which may improve priority handlingfor D2D transmissions. For network controlled radio resource allocationof the SA and/or D2D data on the high priority pool(s), the low priorityD2D devices and channels might not compete for the segregated TDM radioresources. For WTRU autonomous contention resolution on such SA/dataresources, the low priority D2D devices and channels might not competefor the segregated TDM radio resources. For random radio resourceselection of SA/data by D2D terminals, the low priority D2D devices andchannels might not compete for the segregated TDM radio resources.Higher priority D2D data may have a (e.g., significantly) higher chanceof being transmitted successfully during initial determination of radioresources and/or during an ongoing transmission due to reducedinterference from lower priority D2D data. Legacy D2D terminalsincapable of priority handling may be prevented from accessing the newhigher priority SA/data pools through resource segregation.

FIG. 3 is an example diagram of priority based access for D2Dcommunications through TDM of SA in shared D2D data subframes. Prioritybased access for D2D communications may be realized throughTime-Division-Multiplex (TDM) of the SA pools, such as while usingshared D2D data pool(s).

In FIG. 3 , there are N=2 different SA pools and M=1 corresponding D2Ddata pool. The two different SA pools may be defined over differentand/or distinct subframe subsets in time-domain. In FIG. 3 , there areL1=1 subframe for SAs per SA pool per scheduling period of P=160 ms. TheD2D data pool has L2=38 available subframes per scheduling period.

The SA pool (e.g., first SA pool in FIG. 3 ) may carry SAs foraccompanying high priority D2D data transmissions. The SA pool (e.g.,second SA pool in FIG. 3 ) may carry SAs for accompanying lower priorityD2D transmissions.

High-priority D2D data transmissions may be transmitted by (e.g., onlyby) using radio resources from the high-priority SA pool (e.g., first SApool). Lower priority D2D data transmissions may (e.g., may only) betransmitted by using radio resources used for the lower-priority SA pool(e.g., second). SAs from either the high-priority SA pool (e.g., firstSA pool) and/or the lower-priority SA pool (e.g., second) may correspondto D2D data transmitted on the shared radio resources of the D2D datapool.

Priority handling for D2D transmissions may be improve. For example,priority handling for D2D transmissions may be improve if lower priorityD2D transmissions might not occur on the higher priority SA pools. Fornetwork controlled radio resource allocation of the SA on the highpriority pool(s), the low priority D2D devices and channels might notcompete for such segregated TDM radio resources. For WTRU autonomouscontention resolution on such SA resources, the low priority D2D devicesand channels might not compete for such segregated TDM radio resources.For random radio resource selection to determine the SA by D2Dterminals, the low priority D2D devices and channels might not competefor such segregated TDM radio resources. Higher priority D2D data mayhave a (e.g., significantly) higher chance of being transmitted, forexample, due to avoidance of interference and/or contention on the SAradio resources. Priority based access mechanisms may be implementedwhile preserving the principle and/or resource utilization (e.g.,inherent resource utilization) efficiency of shared D2D data pools.

FIG. 4 is an example diagram of priority based access for D2Dcommunications through FDM in the SA and the D2D data subframes.Priority based access for D2D communications may be realized throughFrequency-Division-Multiplex (FDM) of the SA and/or the D2D data pools.

In the example in FIG. 4 , there are N=1 SA pool in time-domain and M=1corresponding D2D data pool in time-domain. In FIG. 4 , there may beL1=2 subframes for the SA per SA pool per scheduling period of P=160 ms.In FIG. 4 , there are L2=38 available subframes in the D2D data pool perscheduling period. The radio resources in the SA pool contain L2=2different and distinct radio block subsets in frequency-domain. Asubframe containing SAs may contain SAs for high priority D2D datatransmission in RBs 10-30, and SAs for low priority D2D data in RBs40-60. Subframes containing D2D data may contain high-priority and/orlow priority transmissions (e.g., only) in RBs 10-30 and RBs 40-60(e.g., respectively). These may be referred to as SA and D2D data poolsin frequency-domain.

The frequency-domain SA pool (e.g., first frequency-domain SA pool inFIG. 4 ) may carry SAs for accompanying high priority D2D datatransmissions in the frequency=domain D2D data pool (e.g., firstfrequency-domain D2D data pool in FIG. 4 ), for example, over theduration of a scheduling period. The frequency-domain SA pool (e.g.,second frequency-domain SA pool in FIG. 4 ) may carry SAs foraccompanying lower priority D2D transmissions in the frequency-domainD2D data pool (e.g., second frequency-domain D2D data pool in FIG. 4 ).

High-priority D2D data transmissions may (e.g., may only) be conductedon radio resources in frequency domain, such as frequency domain used bythe SA (e.g., first SA) and/or the corresponding D2D data pool (e.g.first D2D data pool). Lower priority D2D data transmissions may (e.g.,may only) occur on the radio resources used for the SA (e.g., second SA)and/or the data pool (e.g., second data pool) in frequency-domain. Forexample, an SA carried in a subframe of the high-priority SAfrequency-domain (e.g., first SA frequency-domain) might not announceD2D data on radio resources used with the low priority D2D data (e.g.,second D2D data) frequency-domain. An SA carried in the low-priorityfrequency-domain SA region might not announce D2D data on radioresources in the high priority D2D data frequency-domain (e.g., firstD2D data frequency-domain) region.

Priority handling for D2D transmissions may be improved, for example,when lower priority D2D transmissions might not occur on the higherpriority SA/data frequency-domain pools. Low priority D2D devices and/orchannels might not compete for the segregated FDM radio resources.Higher priority D2D data may have a chance (e.g., significantly higherchance) of being transmitted during determination of radio resourcesand/or during an ongoing transmission, such as a transmission due toreduced interference from lower priority D2D data.

FIG. 5 is an example diagram of priority based access for D2Dcommunications through FDM of SA in shared D2D data subframes. Prioritybased access for D2D communications may be realized throughFrequency-Division-Multiplex (FDM) of the SA pools while using sharedD2D data pool(s).

In FIG. 5 , there is N=1 SA pool in time-domain and M=1 correspondingD2D data pool in time-domain. In FIG. 5 , there are L1=2 subframes forSAs per scheduling period of P=160 ms. In FIG. 5 , there are L2=38available subframes in the D2D data pool per scheduling period. Theradio resources in the SA pool may include L2=2 different and/ordistinct radio block subsets in frequency-domain. A subframe containingSAs may contain SAs for high priority D2D data transmission in RBs10-30, and SAs for low priority D2D data in RBs 40-60. These may bereferred to as SA pools in frequency-domain. Subframes containing D2Ddata may include high-priority and/or low priority transmissions, suchas where designated in one or more (e.g., all) RBs.

The frequency-domain SA pool (e.g., first frequency-domain SA pool inFIG. 5 ) may carry SAs for accompanying high priority D2D datatransmissions, such as in the D2D data pool over the duration of ascheduling period. The frequency-domain SA pool (e.g., secondfrequency-domain SA pool in FIG. 5 ) may carry SAs for the accompanyinglower priority D2D transmissions, for example, in the D2D data pool.

High-priority D2D data transmissions may (e.g., may only) be transmittedby using radio resources from the high-priority SA pool (e.g., first SApool) in frequency-domain. Lower priority D2D data transmissions may(e.g., may only) be transmitted by using radio resources used for thelower-priority SA pool (e.g., second SA pool) in frequency-domain. SAsfrom the high-priority SA pool (e.g., first SA pool) and/or thelower-priority SA pool (e.g., second SA pool) in frequency-domain maycorrespond to D2D data transmitted on the shared radio resources of theD2D data pool.

Priority handling for D2D transmissions may be improved. For example,priority handling for D2D transmission may be improved when lowerpriority D2D transmissions might not occur on the higher priority SAradio resources in frequency-domain. For network controlled radioresource allocation for SA on the high priority pool(s), the lowpriority D2D devices and/or channels might not compete for suchsegregated FDM radio resources. For contention resolution on such SAresources, the low priority D2D devices and/or channels might notcompete for such segregated FDM radio resources. For random radioresource selection to determine the SA by D2D terminals, the lowpriority D2D devices and/or channels might not compete for suchsegregated FDM radio resources. Higher priority D2D data may have achance (e.g., significantly higher chance) of being transmitted, forexample, due to avoidance of interference and/or contention on the SAradio resources. Priority based access mechanisms may be implemented,for example, while preserving the principle and resource utilization(e.g., inherent resource utilization) efficiency of shared D2D datapools.

Priority based access for D2D communications may be realized through TDMand/or FDM of the SA and/or the D2D data pools. The resource pools for(e.g., both) the SA and the D2D data may be segregated in frequencyand/or time.

Priority based access for D2D communication may be realized through TDMand/or FDM of the SA pools, for example, while using shared D2D datapools.

Examples described herein may be extended to the cases of more than twopriority classes with SA or data pools in either time- and/orfrequency-domain. For example, N=M=4 priority categories correspondingto four different and/or distinct subframe subsets for SAs and data maybe used. Radio resource segregation using TDM or FDM may be extended tothe case of more than L1=1 subframes allowed for SA per pool perscheduling period. Different lengths of scheduling periods may be used.SA transmissions may correspond to D2D data transmitted in a laterscheduling period and/or in multiple scheduling periods. For example,independently or in conjunction with scheduling periods, principles ofsemi-persistent, time-limited and/or dynamically granted D2D datatransmissions may be used with TDM and/or FDM principles. Time and/orfrequency resources might not be contiguous. The examples of SA and D2Ddata may be used for illustration purposes. The principles of TDM and/orFDM radio resource segregation may be equally described when usingdifferent D2D channels or signaling messages. For example, D2D discoverymessages may be separated in TDM from D2D control signaling.

Transmission opportunities may be determined, for example, by thefollowing.

D2D transmission opportunities for D2D priority based access using fullor partially segregated TDM/FDM radio resources may be advertised by acontrolling device. The controlling device may be a D2D terminal and/oran LTE radio network device, such as a base station.

A controlling device may signal a set of radio resources (e.g., firstset of radio resources) to be used for high priority D2D datatransmissions. A controlling device may signal a set of radio resources(e.g., second set of radio resources) to be used for lower priority D2Ddata transmissions. Radio resource sets may distinguish betweendifferent types of D2D data and/or control or service messages. Radioresource sets may include different parameter sets for different typesof signaling. The controlling device may signal different sets ofresources and/or, for one or more, or each, set of resources, it maysignal the associated priority levels (e.g., or access classes) that maybe allowed to use the corresponding resources.

The controlling device may (e.g., explicitly) signal those radioresource sets by using a shared control channel, such as a BCH orPD2DSCH broadcast channel. For example, system information on BCH maycontain a combination of either one or both of subframe number orsubframe sets, or frequency resources in combination or association withaccess priority level(s). Such D2D access and/or priority levels may begiven (e.g., explicitly). Such D2D access and/or priority levels may bederived (e.g., implicitly), for example, on the order in which they maybe communicated. Such D2D access and/or priority levels may be given aspart of an index list.

D2D transmission opportunities for D2D priority based access using fullor partially segregated TDM/FDM radio resources may be derived by D2Dterminals, for example, from observing and/or decoding knowntransmission formats and/or reference signals.

A controlling device may set up corresponding radio resource sets insupport of D2D priority based access for use in its vicinity. Forexample, the controlling device may transmit a D2D signal (e.g., firstD2D signal) using a transmission format (e.g., first transmissionformat) in a time/frequency resource (e.g., first time/frequencyresource) for high priority access. The controlling device may transmita D2D signal (e.g., second D2D signal) using a transmission format(e.g., second transmission format) in a time/frequency resource (e.g.,second time/frequency resource) for lower priority access. The D2Dsignal (e.g., first D2D signal) may be an SA using a payload fieldand/or code point to indicate high priority. The D2D signal (e.g.,second D2D signal) may be distinguished from another D2D signal (e.g.,the first D2D signal) through its L1 transmission format, such as thechoice of pilot symbols and/or encoding sequence(s). A D2D terminalintending to transmit and/or receive D2D data may determine accessand/or priority levels for time- and/or frequency resources (e.g.,implicitly) by observing such transmissions from another D2D terminalindicating and/or characterizing high and low priority radio resourcesfrom the controlling device. The controlling device may determine therelationship between observed D2D signals and/or the usedtime-/frequency resources. The D2D terminal may establish a list and/ordatabase that may be representative of transmission opportunities forhigh or low priority D2D data obtained from the occurrences of observedsignals.

D2D transmission opportunities in time or frequency domain for D2Dpriority based access using full or partially segregated TDM/FDM radioresources may be derived by D2D terminals from timing relationship(s),for example, with respect to known and/or observable referencesignal(s).

For example, such a reference signal may be the occurrence(s) of atiming and/or frequency acquisition signal, such as D2DSS, DL SyncSignals, or PD2DSCH. A receiving D2D terminal may determinesoccurrence(s) of such a reference signal. A receiving D2D terminal maycompute expected occurrences in time-domain of transmissionopportunities for high or low priority D2D data. Timing relationshipsmay be implemented and/or given through a formula, for example, using anindex or counter representative of time as one parameter, such as SFN.Timing relationships may be given by a bitmap and/or tabulated set ofvalues. For example, high priority D2D transmission opportunities may begiven in every 8th and 9th subframe, beginning from measured occurrencesof a D2DSS from a transmitter, while low priority transmissionopportunities may be given in every 12th subframe, while being offset by3 subframes from a first D2DSS occurrence.

Examples described herein may be extended to the use of more than twopriority classes, or to the use of different timing relationships ordifferent signaling format representations.

Access mechanisms may be based on the use of radio resource transmissionparameters.

Priority based access for D2D communications may be realized through theuse of different radio resource transmission patterns (RRPTs) for D2Ddata in time- and/or frequency-domain, for example, where RRPTs for usewith high or low priority D2D data may be characterized by differentallocation densities in time/frequency domain over a given time period.

Prioritized D2D access using different radio resource transmissionpatterns may be realized on radio resources used for schedulingassignments (SA), data, control or service signaling such as D2Ddiscovery, for any one of the D2D data signals/channels, or for one ormore (e.g., some) of these D2D data signals/channels in conjunction.

FIG. 6 is an example diagram of priority based access through differentresource allocation densities for D2D subframe pools, such as TDM. InFIG. 6 , different numbers of subframes per scheduling period may beallocated and/or configured with time-domain segregated resources for SAand D2D data for high- and low priority D2D data (e.g., respectively).

In FIG. 6 , a radio resource transmission (e.g., first radio resourcetransmission) pattern (RRTP) may be configured for high priority D2Ddata allowing for 31 D2D data subframes per scheduling period of 160 ms,while a (e.g., second) RRTP for low priority D2D data allowing for 15subframes per scheduling period may be used.

The high-priority SA pool (e.g., first SA pool in FIG. 6 ) and/orcorresponding D2D data pool may allocate a different amount of radioresources per time period, for example one scheduling period, than thelow-priority SA pool (e.g., second SA pool in FIG. 6 ) and/orcorresponding D2D data pool (e.g., almost twice as much).

Priority handling for D2D transmissions may be improved, for example, inthat for the same resource usage efficiency per D2D transmission, lowerpriority D2D transmissions may take longer to complete than highpriority D2D data transmissions. High priority D2D data transmissionsmay make use of more resource allocation space in time and/or frequency(e.g., a “bigger pipe”), which may improve their time to completetransmissions and/or improve upon their observable signal to noiseand/or interference ratios (SINR), such as when compared to the (e.g.,second) low priority SA and D2D data pools.

As shown in FIG. 6 , time-multiplexed SA and D2D data resources may beextended to TDM and may be applied to SA radio resources while (e.g.,only while) using shared D2D data pool(s). The example shown in FIG. 6may be extended to frequency-domain allocations for the SA or the D2Ddata pools, or both.

The example shown in FIG. 6 may be adjusted, for example, by allowingfor radio resource densities in time to be adjusted for differenttransmission characteristics that may be expected for the high prioritySA (e.g., first high priority SA in FIGS. 6 ) and D2D data pools whencompared to those used for the low priority D2D (e.g., second lowpriority D2D in FIG. 6 ) transmission opportunities. For example, ifhigh priority D2D data mainly consists of voice broadcast channelsoccupying 3 PRB's per subframe for which 5 total transmissions per 20 msperiod may be used to sustain an operating SINR of 0-1 dB for BLER attarget levels 2-4%, while low priority D2D data consists of D2Ddiscovery using 2 PRB's and no repetitions to attain detectionreliability against an operating SINR of 5 dB, then the SA and data pool(e.g., first SA and data pool) may be over-dimensioned in an orderapproach (e.g., first order approach), such as by taking (e.g., onlytaking) the number of expected re-transmissions into account for thesame or similar amount of offered traffic, adjusted by anover-provisioning factor for higher priority traffic, as desired.

FIG. 7 is an example diagram of priority based access through differentresource allocation densities (e.g., transmission parameters). In FIG. 7, different numbers of subframes per scheduling period may be used by aD2D terminal with time-domain segregated resources for SA and D2D data,such as while transmitting high- and low priority D2D data (e.g.,respectively).

A radio resource transmission pattern (RRTP) (e.g., first RRTP in FIG. 7) may be used by the D2D terminal for high priority D2D data, while theD2D terminal may use a different RRTP (e.g., second different RRTP inFIG. 7 ) for low priority D2D data.

In FIG. 7 , a shared D2D data pool may be configured. A D2D transmitterintending to send high-priority D2D data, such as voice, may send an SAindicating a, RRTP (e.g., first RRTP) that may result in the use of 28subframes over the Scheduling Period of 160 ms. For the transmission oflower priority D2D data, such as D2D signaling, the D2D transmitter mayuse a distinct or different RRTP (e.g., second RRTP in FIG. 7 ) that mayresult in the use of 19 subframes (e.g., only 19 subframes) over thatsame Scheduling Period.

The high-priority RRTP (e.g. first high-priority RRTP in FIG. 7 ) and/orthe low priority RRPT (e.g., second low priority RRPT in FIG. 7 ) mayallocate different amounts of radio resources per time period, such asone scheduling period.

Priority handling for D2D transmissions may be improved, for example, inthat for the same resource usage efficiency per D2D transmission, lowerpriority D2D transmissions may take longer to complete than highpriority D2D data transmissions. A D2D transmitter device may select(e.g., autonomously select) the amount of radio resources used totransmit D2D data, for example, corresponding to the case of high versuslow priority D2D data. Shared D2D data pools may be used any may improveupon resource utilization and efficiency.

In FIG. 7 , time-multiplexed SA and D2D Data resources may be extendedto frequency-domain allocations for the RRPTs applied to the SA or theD2D data pool(s).

Time- and frequency domain allocations may be combined through the radioresource transmission patterns, for example, to achieve differentallocation densities over a given time period. This may be extended toaccount for different transmission characteristics of D2D data, forexample, as described herein.

Examples described herein (e.g., with respect to FIG. 6 and FIG. 7 ) maybe extended to the cases of more than two priority classes with SA ordata pools in either time- or frequency-domain. For example, N=M=4priority categories corresponding to 4 different and distinct radioresource transmission patterns may be used. Different lengths ofscheduling periods may be used. SA transmissions may correspond to D2Ddata transmitted in later and/or multiple scheduling periods.Independently or in conjunction with scheduling periods, principles ofsemi-persistent, time-limited or dynamically granted D2D datatransmissions may be used with above described principles of differentradio resource transmission densities per time period. While theexamples used SA and D2D data for illustration purposes, the principleof radio resource transmission densities per time period may be equallydescribed when using different D2D channels or signaling messages toimplement priority based access.

D2D transmission opportunities for D2D priority based access usingdifferent radio resource transmission patterns (RRPTs) for D2D data maybe advertised by a controlling device. RRPTs for use with high or lowpriority D2D data may be characterized by different allocation densitiesin time/frequency domain, such as over a given time period. Thecontrolling device may be a D2D terminal. The controlling device may bean LTE radio network device, such as a base station.

A controlling device may signal a set of radio resources (e.g., firstset of radio resources) with a (e.g., first) radio resource allocationdensity over a time period for use with high priority D2D datatransmissions. A controlling device may signal a set of radio resources(e.g., second set of radio resources) with a different radio resource(e.g., second different radio resource) allocation density over a timeperiod for use with lower priority D2D data transmissions.

The controlling device may (e.g., explicitly) signal those radioresource sets, for example, by using a shared control channel, such as aBCH or PD2DSCH broadcast channel. System information on BCH may containa combination of one or both of subframe number or subframe sets, orfrequency resources in combination, or association with access prioritylevel(s). Such D2D access and priority levels may be given (e.g.,explicitly), may be derived (e.g., implicitly) on the order in whichthey are communicated, may be given as part of an index list, or may bederived by the order in which they are communicated.

D2D transmission opportunities for D2D priority based access may bedetermined by a transmitting D2D terminal, for example, in the form ofdistinct radio resource transmission patterns (RRPTs) for D2D data, suchas where the RRPTs for use with high or low priority D2D data may becharacterized by different allocation densities in time/frequency domainover a given time period.

A D2D transmitter device intending to transmit D2D data may (e.g.,first) determine whether its D2D data corresponds to the category ofhigh priority data or to low priority data. The D2D transmitter maydetermine the corresponding SA and/or data radio resources for use withits D2D data transmission, for example, as an outcome of thedetermination of priority. The D2D transmitter device may select an RRPT(e.g., first RRPT) to be used for high priority D2D data, or an RRPT(e.g., second RRPT) to be used for low priority data, such as where theRRPTs are characterized by different allocation densities intime/frequency domain over a given time period. The D2D transmitter maytransmit SA and/or D2D data on the determined radio resources.Transmission of SA and D2D data may terminate, for example, when thereis no more data to transmit. A re-evaluation and/or determination ofappropriate radio resources may be conducted, for example, when theremay be a change to radio resources allowed for the high or low prioritySAs, or when a new scheduling period begins.

A D2D receiver device intending to decode D2D data may determine SAand/or data radio resources. The D2D receiver may determine whether highpriority or low priority D2D transmissions may be received on thecorresponding radio resources. The D2D receiver may determine a radioresource transmission pattern (RRTP) that may be representative of theaccess priority of D2D data, such as may be indicated or decoded orderived from the D2D signal transmission. As a function of the RRTP, theD2D receiver may attempt to decode and/or demodulate at least the subsetof radio resources, for example, as a function of the determinedparameters.

Different radio resource transmission patterns (RRPTs) for D2D datausing prioritized access may be determined by a transmitting D2Dterminal, for example, from timing relationship(s). RRPTs for use withhigh or low priority D2D data may be characterized by differentallocation densities in time/frequency domain, for example, over a giventime period.

For example, when using a reference signal to determine timingparameter(s), these may be the occurrence(s) of a timing and/orfrequency acquisition signal, such as D2DSS, DL Sync Signals, orPD2DSCH. A transmitting D2D terminal may determines an RRPT (e.g., firstRRPT), such as a baseline pattern with respect to the occurrence(s) ofthe timing reference. The transmitting D2D terminal may determine anadjusted RRPT (e.g., second adjusted RRPT) for use for its D2Dtransmission, for example, by using the determined RRPT as an input(e.g., first input) and a parameter whether D2D data is high or lowpriority as an input (e.g., second input). Timing relationships may beimplemented or given through a formula using an index or counterrepresentative of time as one or more parameters, such as SFN. Timingrelationships may be given by a bitmap or tabulated set of values. Forexample, high priority D2D transmission opportunities may be determinedfrom a baseline RRPT pattern resulting in transmission in every fourthsubframe, beginning from measured occurrences of a D2DSS from atransmitter, while low priority transmission opportunities may bedetermined (e.g., only) for every 12th subframe, while being offset bythree subframes from a first D2DSS occurrence.

Examples described herein may be extended to the use of more than twopriority classes, or the use of different timing relationships.

Access mechanisms may use guaranteed segregated resources for highpriority devices.

The priority access may be performed by guaranteeing and/or potentiallyreserving a set of resources that may be used by higher priority datatransmissions. The resources may correspond to a set of time/frequencyresources for SA and/or data pools (e.g., including a set of patterns).Higher priority WTRUs may have guaranteed access to these resources,Lower priority WTRUs may use the high priority reserved data resources,for example, if those resources are not being used by high prioritydata.

The SA resource pools may be segregated in time and/or frequency fordifferent priority access WTRUs and/or data transmissions. For example,the first N SA subframes in a scheduling period may correspond tosubframes that may be used by (e.g., only by) devices transmitting highpriority data and/or devices that may be high priority devices.

A WTRU may monitor the resources (e.g., SA resource/subframes)configured for transmission of data with higher priority than theavailable data in the WTRU. The WTRU may monitor the subframes reservedfor higher priority data transmissions.

If the WTRU determines that at least X (e.g., where X may be aconfigurable number) higher priority scheduling occurrences may bedetected on the higher priority SA resources (e.g., in the current orpast scheduling period(s), e.g., over a predefined window), the WTRU maytransmit the lower priority data on (e.g., only on) the resource pool(s)reserved/configured for the low priority data. If the WTRU determinesthat at least X higher priority scheduling occurrences may be detectedon the higher priority SA resources, the WTRU may transmit (e.g., onlytransmit) using one or more (e.g., one) of the RRPTs selected from thelist of RRPT to be used for low priority data or configured for thepriority level of the available data for transmission. This may ensurethat, if there is at least one high priority data transmission, thelower priority WTRUs might not attempt to use the resources for higherpriority data. If less than X scheduling occurrences are detected, theWTRU may select resources from the data resource pool configured forhigher priority data and for lower priority data. If less than Xscheduling occurrences are detected, the WTRU may select from the listof RRPTs reserved for higher priority data and for lower priority data.

The WTRU may (e.g., first) decode the SAs transmitted on the highpriority SA resources and determine the set of resources or set of RRPTsused by the high priority data. The WTRU may exclude the set ofresources or set of RRPTs used by the high priority data from the listof available RRPTs or available resources to use. This may allow a WTRUtransmitting lower priority data to make use of resources that might notbe used to transmit higher priority data.

4 SA subframes per Scheduling period of 80 ms may be configured for D2Dtransmissions. The set (e.g., complete set) of SA subframes 1-4 may beused for transmission and/or reception by WTRUs, e.g., for high priorityD2D data. The subset of SA subframes 3-4 may be used by WTRUs for lowpriority D2D data (e.g., only the subset of SA subframes 3-4 may be usedby WTRUs for low priority D2D data). A WTRU may (e.g., first) determinewhether the D2D data it has to transmit is high or low priority D2Ddata. If the WTRU determines that its D2D data is low priority, the WTRUmay determine whether high priority D2D transmissions by other WTRUs areannounced for the Scheduling period from decoding SAs in the 4 availableSA subframes. If it finds such high priority SAs, it may extractdecoding information and/or determine transmission parameterscorresponding to these high priority SAs. The WTRU may determine a setof D2D SA and corresponding D2D data subframes currently in use by otherhigh priority WTRUs. The WTRU may select SA and/or D2D data resourcesnot in use by a determined high-priority WTRU (e.g., all determinedhigh-priority WTRUs) and transmit its own SA. If no available SA and/orD2D data resource can be found, its transmissions may be deferred. If,e.g., as described herein, the WTRU determines that its D2D data is highpriority, it may select an available SA and corresponding D2D dataresource for its own transmission (e.g., any available SA andcorresponding D2D data resource for its own transmission).

In one or more techniques described herein, perhaps for example if thenumber of high priority WTRU transmissions decoded by the low priorityWTRU may be larger than some value N, among other scenarios, the lowpriority WTRU may behave using one or more of the following:

-   -   Transmit on another SA pool and/or data pool in the same        scheduling period;    -   Use the same SA pool, but transmit on another data pool in the        same scheduling period;    -   Use the same SA and/or data pool in the same scheduling period,        but transmit using a TRPT and/or time frequency resources for SA        that might not be used by any of the high priority WTRUs,    -   Reduce transmit power in the current scheduling period;    -   Defer transmission to the next scheduling period and/or some        random time in the future; and/or    -   Start a retransmission timer, which, in some techniques, perhaps        after expiry, the WTRU may retry one or more of the        aforementioned, for example, among other scenarios.

In some embodiments, for example concerning the SA resources, perhaps toavoid collision of SA resources and/or perhaps to allow SA resources tobe more readily accessible by the high priority users, among otherscenarios, the SA subframes usable for high priority may occur(partially or completely) first in time (e.g., as compared to the lowpriority SAs). The SA resources associated to high priority WTRUs and/orthose associated to low priority WTRUs may be configured in the WTRUsvia signaling (e.g., by being assigned to different SA pools), and/orcould be statically configured in one or more, or all, WTRUs.

For example, the set of SA resources (0<=N PUCCH<N2) configured assubframe resources and/or resource blocks for a specific transmit poolcould be separated into two sets where 0<=N_PUCCH<N1 may be reserved forthe high priority user and N1<=N_PUCCH<N2 may be reserved for the lowpriority user (e.g., resources in earlier subframes may have smaller orthe same N_PUCCH index). Perhaps when the high priority WTRU transmitsusing the specific pool, the WTRU may randomly select and/or utilize theSA resources reserved for the high priority users (and perhaps in sometechniques only such resources).

A WTRU with high priority (e.g., a first priority) may select and/orutilize any SA resource configured for D2D SA transmission in a givenscheduling period. A WTRU with low priority (e.g., a second priority)may utilize any SA resources which might not be part of the SA resourcesreserved for the high priority transmissions. The low priority WTRUs maymake such determination by decoding the SAs associated to high priorityWTRUs.

For example, the first N1 time frequency blocks which can be chosen by ahigh priority WTRU may occur (e.g., may always occur) prior in time tothe first N2 time frequency blocks which can be chosen by a low priorityWTRU. In other words, N1 for the high priority WTRU may be in the set0<N1<K1, while N2 for the low priority WTRU may be anywhere in N1>N2>K2.For example, the parameters N1, N2, K1, and/or K2 may refer to a timeindex such as subframe numbers or indices. A first SA pool for highpriority WTRU transmissions may be available in subframes numbered from0 to K1=3. A second SA pool for low priority WTRU transmissions may beavailable in subframes numbered from 0 to K2=8. Perhaps when a lowpriority WTRU might not detect a high priority WTRU transmission insubframes N1=0, 1 and/or 2, among other scenarios, it may utilize an SAresource in subframes N2>2. For example, the parameters N1, N2, K1,and/or K2 may refer to a time-frequency index such as identified asnumbered and/or indexed RB/subframe time-frequency resources. A first SApool for high priority WTRU transmissions may be available in subframesnumbered from 0 to K1=2 and in 50 RBs per subframe, one or more, oreach, yielding 150 indexed RB/subframe time-frequency resources. Asecond SA pool for low priority WTRU transmissions may be available insubframes numbered from 0 to K2=5 using 20 RBs per subframe, one ormore, or each, yielding 120 indexed RB/subframe time-frequencyresources. Perhaps for example when a low priority WTRU might not detecta high priority WTRU transmission in the 150 indexed high priorityRB/subframe time-frequency resources, among other scenarios, it mayutilize an SA resource in the 120 indexed low priority RB/subframetime-frequency resources.

A WTRU with low priority transmissions may use (e.g. at least a part of)the SA resources for a scheduling period which are reserved for highpriority WTRUs, perhaps for example after the WTRU with low prioritytransmissions may determine that these resources might not be used,among other scenarios. For instance, if an SA (initial transmissionand/or retransmissions) includes at least 2 distinct time/frequencyblocks which are associated together, the WTRU with low prioritytransmissions, perhaps for example after determining that the firstPUCCH transmission may be unused, can use the remaining PUCCHtransmission which may belong to the high priority WTRU transmission.The WTRU may transmit with one or more of: fewer repetitions, modifiedtransmit power, and/or reduced MCS. The low priority WTRU, perhaps forexample when having determined that there are no transmissions by thehigher priority WTRU, among other scenarios, may utilize the SAresources not reserved for low priority WTRUs. Determination of whichselection to make may be a random decision, perhaps for example based onsome signaled criteria, and/or may be based on channel measurements.

A WTRU may apply the same or different behavior in the example describedherein on one or more transmit pools, and perhaps in some scenarios maydo so simultaneously. For instance, a low priority WTRU may listen forhigh priority transmissions in one or more, or multiple, pools perhapsbefore selecting the pool on which to transmit. Different pools may havedifferent reservation rules for the SA resources between high and/or lowpriority WTRU transmissions (e.g., a pool 1 may have one or moredistinct SA resources for high and/or low priority while pool 2 mightnot).

Using features described herein, high priority D2D transmissions mayhave preferential access (e.g., first access) to configured and/oravailable D2D transmission resources. Low priority D2D transmissions maybe selected as a function of these and are may be transmitted if D2Dtransmission resources are still available. Given that WTRUs may bedecoding incoming SA in SA carrying subframes to determine whether theymay receive corresponding D2D data as part of monitored talk groups,using available information obtained from decoding SAs to determinewhich D2D transmission resources are occupied may come at little addeddecoding complexity.

In some embodiments, specific resources may be reserved for highpriority transmissions and/or the high priority WTRUs may transmit anoccupancy flag to indicate to the low priority WTRUs that they may usethe high priority SAs and/or data resources for a given schedulingperiod. The occupancy flag may be transmitted as part of the SA (e.g.,at the beginning of the SA), and/or could be transmitted in an SA inadvance of the target scheduling period, perhaps for example to indicatethe occupancy of one or more SA resources in one or mode futurescheduling periods. The occupancy flag may be transmitted in a separatechannel (e.g. D2DSS and/or PD2DSCH) that may be read by one or more, orall D2D WTRUs. A flag may be associated with a (e.g., a single) SAresource, with a pool and/or resources, and/or with one or more, or all,resources available for transmission of D2D.

For example, 4 SA subframes per scheduling period of 80 ms may beconfigured for D2D transmissions. A (e.g., a single) occupancy flagassociated to subframes 1 and 2 can be set whenever a high priority WTRUmay utilize either of these subframes. A low-priority WTRU may wish totransmit SA and/or (e.g., subsequently) data. The WTRU may check for thepresence of the occupancy flag, perhaps for example, to determinewhether there are any higher priority WTRUs planning to transmit SA forthat scheduling period. When the occupancy flag is set, among otherscenarios, the lower priority WTRUs may be utilize (e.g., may onlyutilize) subframes 3 and 4. When the occupancy flag is not set, amongother scenarios, the lower priority WTRU can select any SA resource(s)for transmissions.

For example, a high priority WTRU which may have selected resource(s) ona scheduling period x (e.g., and/or indicated this using the occupancyflag), may also indicate that it may re-use the same SA resource(s)and/or data (e.g., RRPTs) on the following SA period. In such scenarios,among others, a low priority WTRU might not use the high priorityresources for the next two scheduling periods, for example.

A WTRU may be configured (e.g., by the eNB and/or ProSe function) and/ormay be pre-configured to be allowed to transmit an occupancy flag thatmay be destined to the low-priority users. For example, a WTRU may beconfigured to be used by a “special user” (police chief, fire chief,etc.). A WTRU, perhaps for example under certain circumstances and/ortriggers (e.g. an emergency situation), may (e.g., may be allowed) totransmit the occupancy flag. This trigger may allow the WTRU to do sofor a period of time, perhaps for example a finite period of time.

In some embodiments, the WTRU may measure and/or determine the signalstrength and/or signal occupancy of the set of resources for SA and/orset of RRPTs that may be reserved for the high priority data. The WTRUmay transmit (e.g., may only transmit) on those resources, perhaps forexample if the signal strength and/or signal occupancy is below somepre-defined and/or known threshold. Measurement may be made at the timeinstant and/or scheduling period in which the WTRU may wish to transmit,and/or they may include a measurement made on a past scheduling periodand/or averaged over several scheduling periods in the past. Themeasurement may include a measurement and/or RSSI and/or similaroccupancy or interference measurement. The thresholds may be staticallydefined, and/or they may be configured in the WTRU via RRC signalingand/or via PHY-layer signaling in a D2D Synchronization Channel(PD2DSCH).

For example, 4 SA subframes per scheduling period of 80 ms may beconfigured for D2D transmissions. The complete set of SA subframes 1-4may be used for transmission and/or reception by WTRUs for high priorityD2D data. The subset of SA subframes 3-4 (e.g., only such a subset) maybe used for WTRUs for low priority D2D data. A WTRU may determinewhether the D2D data it may wish to transmit is high or low priority D2Ddata. If the D2D data is low priority, among other scenarios, the WTRUmay check the signal occupancy of SA subframe 1 and/or 2. This signaloccupancy could be an averaged measurement of RSSI over the last Nsubframes, for example. If the signal occupancy measure of either ofthese subframes is below a threshold, the WTRU having low priority datato transmit may select that subframe for transmission. If the occupancymeasure is above a threshold, among other scenarios, the WTRU with lowpriority data to transmit may use subframes 3 and/or 4 for transmission.A WTRU that may determine that it has high priority D2D data totransmit, among other scenarios, may transmit using SA subframe 1 and/or2, or may transmit on any of the 4 SA subframes.

In some embodiments, there may be different priority levels,correspondingly different SA subframes, and/or different thresholds. AWTRU with the lowest priority level (e.g., out of 4 levels) may checkthe occupancy measure for one or more, or each, of the 4 subframes. Ifthe occupancy level of any of the 4 subframes is below the correspondingthreshold for that subframe, among other scenarios, the WTRU maytransmit on any of the subframes where the occupancy level was below athreshold. If none of the SA subframes meets this criteria (e.g., at anytime), among other scenarios, the WTRU with low priority data totransmit may defer its transmission to the next SA period and/or mayrepeat the described techniques.

In one or more techniques, one or more, or a set, of SA and/or dataresources may be reserved. High priority WTRUs, perhaps when utilizingsuch resources, among other scenarios, may transmit with higher powerthan the low priority WTRUs. WTRUs with high priority transmissions mayuse (e.g., may be restricted to use) these reserved resources. WTRUswith high priority transmissions may use one or more, or all, resources,perhaps while respecting the transmission power values associated withthe high priority WTRUs. WTRUs with low priority transmissions may useone or more, or all, resources (e.g., reserved and/or non-reserved),perhaps while respecting the transmission power values associated withthe low priority WTRUs. One or more techniques in which the low priorityWTRUs may transmit with lower transmit power on resources reserved forthe high priority WTRUs may be used in combination with other techniquesdescribed herein.

In one or more of the techniques described herein, the guaranteedsegregated resources for the high priority WTRUs may be signaled by thenetwork (e.g., via RRC, NAS, and/or MAC signaling), and/or could bestatically determined and/or defined. They may be defined/determined bythe ProSe function. The presence of guaranteed segregated resources maybe determined dynamically by one or more, or each, WTRU, perhaps basedon one or more rules, and/or might not be the same for all WTRUs. Forexample, a low priority WTRU may determine that the segregated resourcesmay be present on a given scheduling period, perhaps for example basedon measurements made of the current and/or previous scheduling period,and/or current and/or past determination(s) of the presence of highpriority WTRUs. For example, low priority WTRUs may respect the rulesassociated with one or more segregated resources on these schedulingperiods, perhaps for example while operating using normal Release 12rules on scheduling periods where such determination(s) may indicatethat there might not be any segregated resources present.

Features described herein may use a specific and/or limitedconfiguration using SA subframes; the operational principle may beextended to D2D subframes other than SA, such as including D2D subframesand/or frequency regions allowed for D2D transmission. Featuresdescribed herein may be applied for the case of more than 2 prioritylevels, e.g., more than low and high, e.g., low, medium, and high, arange of priorities, etc. The features described herein (e.g., tieredD2D transmission resources to allow for higher priority WTRUs to usetime/frequency resources first, and lower priority WTRUs to choose theirown D2D transmission resources in time/frequency after determining(e.g., only after determining) which ones are announced in use by higherpriority WTRUs) may be applied to other D2D signals and/or channelsother than SA.

Access mechanisms for D2D control and data may be provided.

D2D data transmissions carrying control signaling may be received and/ortransmitted by a WTRU in a set of designated time/frequency resources.

D2D control signaling may refer to application layer control messagesexchanged between D2D WTRUs for the purpose of floor control, sessioncontrol, connection establishment and/or similar purposes, e.g., toadminister group calls. D2D control signaling may correspond to radiomessages used for the purpose of managing D2D connections and receptionand/or transmissions in WTRUs. Control signaling at application layermay be a self-contained D2D PDU, or it may be multiplexed with D2D datasuch as carrying VoIP packets or segments thereof.

A set of designated time/frequency resources for transmission and/orreception of D2D control messages may be obtained from one or more ofthe following parameters: timing values such as frame or subframecounters; cell-wide or D2D system frame values; timing offset value(s)applied to a reference subframe or frame; offset applied tooccurrence(s) of a selected cell-wide or D2D signal or channel;frequency indices, RBs, or group of frequency regions; cell-wide or D2Dsystem or WTRU identifier; group communication identifier; or channel orgroup index value(s).

Some or all parameters may be pre-configured in the WTRU, or they may beobtained through configuration signaling during system operation, orthey may be derived by the WTRU by means of a lookup table or formula orequivalent. The WTRU may derive D2D transmission resources as a limitedand/or designated subset of the available D2D transmission resources,e.g., after determining D2D subframes, allowed frequency regions, etc.

The WTRU may transmit or receive a D2D control message in a set ofselected and/or reserved subframes that may comprise a subset ofpossible D2D data subframes. When a scheduling period of 40 ms is used,every 4th scheduling period may include D2D control messages orsignaling e.g., for either one, selected or possibly one or more, oreach, D2D communication group.

A set of time/frequency transmission patterns may be used fortransmission and/or reception of D2D control messages. The set oftransmission patterns may be pre-determined and/or fixed, or it may bederived by a D2D WTRU, e.g., as a function of D2D transmissionparameters. When 64 possible transmission patterns are obtainedfollowing D2D data subframe allocations, the first 7 of those (e.g.,only the first 7 of those) may be used for the purpose of transmittingD2D control signaling associated with a D2D communication group. Usingfeatures described herein, useful and/or time-critical D2D controlsignaling may make use of reserved D2D transmission resources in thesystem, e.g., it might not be interfered or suffer from lack oftransmission opportunity when D2D data such as VoIP is concurrentlytransmitted in the D2D transmission resources.

A D2D transmitter device may transmit D2D data. For examples describedherein, a D2D transmitter device intending to transmit D2D data maydetermine (e.g., first determine) the highest priority data availablefor transmission and the associated priority level of D2D data. The WTRUmay determine the priority level of the WTRU (e.g., a high priorityWTRU). The D2D transmitter may determine the corresponding SA and/ordata radio resources for use with its D2D data transmission, forexample, as an outcome of the determination of priority. The D2Dtransmitter may transmit SA and/or D2D data on the determined radioresources. The WTRU may determine the D2D data resources it may use, forexample, as a function of resources used by higher priority users in thesystem. Transmission of SA and D2D data may terminate, for example, whenthere is no more data to transmit. A re-evaluation and/or determinationof appropriate radio resources may be done, for example, when there maybe a change to radio resources allowed for the high or low priority SAs,or when a new scheduling period may begin or when a time-limited grantmay expire.

A D2D receiver device may receive D2D data. A D2D receiver deviceintending to decode D2D data may determine SA and/or data radioresources. A D2D receiver device may determine whether high priority orlow priority D2D transmissions may be received on the correspondingradio resources. The D2D receiver device may attempt to decode one ormore, or all, and/or (e.g., only) a selected subset of radio resourcesdetermined as a function of parameters, such as D2D services that may bereceived. For example, if there is an ongoing high priority D2D datatransmission to be received by the device, it may choose to not receiveon radio resources corresponding to the lower priority SA/data pool, forexample, if there are receiver processing constraints. For example, ifthe device may be configured to receive selected (e.g., only certainselected) types of D2D signals/channels, such as low priority backgroundservice signaling, it may forego reception and/or processing of radioresources corresponding to the high priority SA/data pools. The D2Dreceiver device may uses the determined radio resources to demodulateand/or process the D2D data transmissions.

Priority based access may utilize contention resolution of radioresources.

Priority based access for D2D communications may be realized through theuse of persistence parameter(s), for example, while determiningtime/frequency resources for D2D transmission.

Persistence parameter(s) for use with prioritized D2D access may beassociated with radio resources for scheduling assignments (SA), D2Ddata, control or service signaling such as D2D discovery, for example,for one or more of D2D data signals/channels or for one or more or someD2D data signals/channels. The use of persistence parameter(s) may becombined with different resource selection approaches, such as randomresource selection, channel busy measurements, or resource allocation bymeans of D2D grants.

FIG. 8 is an example diagram of priority based access for D2D data usingpersistence parameters (e.g., SA). In FIG. 8 , persistence parametersmay be used by a D2D transmitter device with D2D data to transmit todetermine if radio resources may be used by the transmitter device, andif they may be used, determine the SA resources that may be used forpriority based D2D data at the beginning of a scheduling period.

The D2D transmitter intending to transmit D2D data may determine a setof available SA resources. The D2D transmitter may determine which SAresources may be available by different means, such as from receivedconfiguration signaling, from pre-stored information, and/or fromchannel measurements. For SA resources deemed available, the D2Dtransmitter may draw a random number from 0 . . . 1 for one or more(e.g., every) SA access opportunity. The D2D transmitter may compare ifthe random number drawn for a given SA access opportunity is higher thana threshold value, such as for high priority data (e.g., PH=0.2). Ifyes, it may choose to transmit any high priority D2D data on resourcescorresponding to the SA in that access opportunity. If the D2Dtransmitter has low priority D2D data to transmit, it may (e.g., only)consider a given SA access opportunity valid, for example, if the randomnumber drawn is higher than a threshold value (e.g., PH=0.8). If as anoutcome, the D2D transmitter determines one or more valid accessopportunity, it may transmit on such a selected SA access opportunity.The D2D transmitter may repeat the above for a next upcoming SA resourcepool.

The D2D transmitter may (e.g., on average) determine a number (e.g.,around 60%) of SA access opportunities as valid, for example, for (e.g.,exclusive) transmission of any high-priority data. The D2D transmittermay determine a number (e.g., 20%) as valid for any low and/or highpriority data. The D2D transmitter may deem a number (e.g., 20%) of SAaccess opportunities as barred.

The use of persistence parameters may statistically result in highpriority D2D data being allowed to be transmitted by a D2D terminal(e.g., significantly) more often than low priority D2D data. Prioritybased access for D2D communications may be improved by making the higherpriority data (e.g., control signaling) and/or users win resourceselection of SA and/or data more often than lower priority users.

FIG. 8 may be extended to more than two priority classes with SA or datapools. For example, persistence parameters associated with N=4 prioritycategories may be used. Access opportunities for D2D data transmissionmay be construed from a set of time/frequency resources determinedand/or signaled and/or limited to within different subframes and/orfrequency regions. The list of available resources may be obtained frompreceding measurements and/or channel observations. The examplesdescribed herein may be extended to persistence parameters associatedwith subframes and/or counters and/or indices representative of timerather than D2D access opportunities in frequency-domain. Time and/orfrequency resources might not be contiguous.

The principles described herein may equally apply independently or inconjunction with one or multiple scheduling periods, forsemi-persistent, for time-limited or for dynamically granted D2D datatransmissions. While examples described herein may be used in thecontext of SA access opportunities, the use of persistence parametersassociated with D2D access opportunities may equally be applied to D2Ddata subframes and/or for using different D2D channels or signalingmessages. For example, priority based access for D2D discovery messages,as opposed to D2D control signaling, may be determined as describedherein.

Priority based access for D2D communications may be realized through theuse of persistence parameter(s), for example, while determining validtime/frequency resources for D2D transmission.

A D2D transmitter device may determine whether a D2D transmissionopportunity may be allowed, for example, as a combination of a channelmeasurement in conjunction with persistency parameters. The channelmeasurement may be substituted by a (e.g., random) selection ofcandidate D2D transmission opportunities.

Persistence parameter(s) for use with prioritized D2D access may beadvertised by a controlling device. The controlling device may be a D2Dterminal. The controlling device may be an LTE radio network device,such as a base station.

A controlling device may signal a set of persistence parameters (e.g.,first set of persistence parameters) associated with radio resources tobe used for high priority D2D data transmissions. A controlling devicemay signal a set of persistence parameters (e.g., second set ofpersistence parameters) radio resources to be used for lower priorityD2D data transmissions. Persistence parameters may distinguish betweendifferent types of D2D data and/or control or service messages, and mayinclude different parameter sets for different types of signaling.

The controlling device may (e.g., explicitly) signal those radioresource sets by using a shared control channel, such as a BCH orPD2DSCH broadcast channel. System information on BCH may contain acombination of one or both of subframe number or subframe sets, and/orfrequency resources in combination or association with persistenceparameters. Persistence parameters may be given (e.g., explicitly).Persistence parameters may be derived (e.g., implicitly) on the order inwhich they are communicated. Persistence parameters may be given as partof an index list.

Persistence parameter(s) for use with prioritized D2D access may beadjusted by a D2D terminal, for example, as a function of one or more ofthe following: observed signal conditions, channel measurements, sensingof transmission collisions and/or interference, detection oftransmissions by higher priority WTRUs, timing and/or counter values(e.g., based on data latency requirements), and/or signaling events.

A transmitting D2D terminal may determine (e.g., determine in a firstinstance) that no D2D access opportunity may be allowed, for example, asan outcome of the persistency check. The transmitting D2D terminal maydefer an attempt for its D2D transmission to a (e.g., second) later timeinstant. The D2D transmitter may decrease the threshold value for lowpriority access to a lower value (e.g., to PL=0.7). This may be the caseif, for example, a certain condition is met (e.g. based on signalconditions, timing or counter value, signaling events, etc.). If duringthe (e.g., second) later time instance it still fails to transmit itslow priority data, it may decrease the threshold to a lower value, forexample, to 0.6. If in a (e.g., third) later time instance it succeedsin transmitting low priority D2D data, the D2D terminal may reset thethreshold to the initial value, for example, PL=0.8, for any (e.g.,subsequent) initial attempt to transmit low-priority data.

Persistence parameters may be adjusted by a D2D transmitter, forexample, as a function of one or more (e.g., one) of the followingevents or observations, successful or failed access attempts, availableabsolute or relative D2D traffic volume in queue(s), timer or countervalues at expiry (e.g. for delay-sensitive traffic or to meet latencyrequirements) or as a function of preceding D2D data transmission orreception events, received signal strength of signals or channelsreceived from other D2D terminals or LTE infrastructure nodes, etc.Adjustment of persistence parameters by a D2D terminal may occurseparately for different types of D2D data transmission, such as a setof persistence parameters (e.g., first set of persistence parameters)subject to continuous monitoring and/or updates for D2D controlsignaling, a set for D2D high priority data (e.g., second set for D2Dhigh priority data), a set of persistence parameters (e.g., third set ofpersistence parameters) being adjusted as a function of signalconditions, events or timer/counter conditions for D2D Discovery, etc.

The persistence parameters applicable to a type of transmission for aD2D terminal may be adapted as a function of property(ies) of receivedD2D signals, e.g., transmitted by other terminals. Such signals may ormight not be intended for the D2D terminal adapting the persistenceparameters. The properties may include one or more of the following: apropriety related to the number of D2D transmissions received over aperiod of time, possibly from a specific channel (e.g., PSCCH or PSSCH);or a priority level associated to at least one received D2Dtransmission.

A WTRU may decrease a persistence parameter applicable to a type oftransmission, e.g., if it receives at least one D2D transmission (or itsassociated SA). The received D2D transmission may have to satisfy atleast one of the following conditions: the priority level of thereceived D2D transmission may have to be higher than, or equal to orhigher than, the priority associated to the type of transmission; thereceived D2D transmission may have to be received no more than a certainduration after the last received D2D transmission, possibly of the sameor higher priority; a group destination ID, source or destination IDassociated to the received D2D transmission may have to match certainvalue(s); the resource from which the D2D transmission was received(e.g., resource pool) may have to match one of a set of resources, suchas a resource pool associated to the type of transmission to which thepersistence parameter is applicable.

A priority level of a received D2D transmission may be obtained from oneor more of the following: a field included in sidelink controlinformation (e.g., in a PSCCH), such as an explicit indication ofpriority, or a Group destination ID that may be associated to a prioritylevel; a field in a MAC header of a transport block decoded from PSSCH,such as an explicit indication of priority, or a source or destinationidentity associated to a priority level; a resource from which the D2Dtransmission was received (e.g., resource pool and/or T-RPT).

For one or more, or each, received D2D transmission the persistenceparameter may be decreased by a first step size. The persistenceparameter may be increased by a second step size (e.g., which maytypically be smaller than the first step size) at regular intervals,such that its value e.g., gradually restored to a higher level inabsence of received D2D transmission. The WTRU may periodicallydetermine a value of the persistence parameter based on the number ordensity of received D2D transmission (or equivalently SAs) over a pastevaluation period, or equivalently based on the estimated load on theD2D resources (e.g., based on estimated average SINR, or other).

The WTRU may receive the value of the persistence parameter from a fieldin PSCCH or PSSCH of the received D2D transmission and may apply thisvalue if it is lower than the current value and/or until a timer startedupon reception of this transmission expires.

The persistence parameter may be constrained to be within a definedrange, e.g., such that it cannot decrease below a certain value (orincrease above a certain value) even if one of the above conditions issatisfied.

Supporting parameters may be configured by higher layers, pre-defined,or pre-configured. Such supporting parameters may for instance includeone or more of step sizes, intervals, duration of evaluation period,persistency values (e.g., possibly for one or more, or each, value of areceived field if applicable), corresponding intervals of the number ofreceived transmission within an evaluation period, or minimum andmaximum values.

Properties of received D2D signal(s) as described herein may determinethe selection of a resource pool among a set of candidate resources(e.g., which may be in addition to persistence parameters). For example,the WTRU may select a resource pool that maximizes or minimizes acertain metric, where the metric may be a function of the received D2Dtransmissions on the resource pool. The metric may be evaluatedsimilarly as described for the persistence value herein (e.g., decreasewhen the number of received D2D transmissions in a period of time ishigher).

Persistence parameters applicable to a type of transmission for a D2Dterminal may be adjusted as a function of properties of received D2Dsignal(s) transmitted by one or more other terminals. Such signals mayor might not be intended for the D2D terminal adapting the persistenceparameters. A Property of a received D2D signal may include one or moreof: a property related to the number of D2D transmissions received overa period of time, for example possibly from a specific channel (e.g.,PSCCH or PSSCH); or a priority level associated with at least onereceived D2D transmission.

One or more persistence parameters may be adjusted based on a receivedD2D transmission. For example, a WTRU may decrease a persistenceparameter applicable to a type of transmission if it receives at leastone D2D transmission. The received D2D transmission may satisfy at leastone of the following conditions: the priority level of the received D2Dtransmission is higher than, or equal to or higher than, the priorityassociated to the type of transmission; the received D2D transmission isreceived no more than a certain duration after the last received D2Dtransmission (e.g., of the same or higher priority); a group destinationID or source or destination ID associated with the received D2Dtransmission matches a certain value(s); the resource from which the D2Dtransmission was received (e.g., resource pool) matches one of a set ofresources, such as a resource pool associated with the type oftransmission to which the persistence parameter is applicable.

A priority level of a received D2D transmission may be obtained from oneor more of the following: a field included in sidelink controlinformation (e.g. in a PSCCH), such as an explicit indication ofpriority, or a Group destination ID that may be associated with apriority level; a field in a MAC header of a transport block decodedfrom the PSSCH, such as an explicit indication of priority, or a sourceor destination identity associated with a priority level; a resourcefrom which the D2D transmission was received (e.g., resource pool and/orT-RPT).

One or more persistence parameters may be adjusted based on a receivedD2D transmission. One or more of the following examples may apply.

When a D2D transmission is received, the persistence parameter may bedecreased by a first step size (e.g., this may occur one or more, oreach, time a D2D transmission is received). The persistence parametermay be increased by a second step size (e.g., which may typically besmaller than the first step size) at regular intervals, such that itsvalue may gradually be restored to a higher level in the absence ofreceived D2D transmission(s).

The WTRU may periodically determine a value of the persistence parameterbased on the number of received D2D transmission(s) over a pastevaluation period.

The WTRU may receive the value of the persistence parameter from a fieldin PSCCH or PSSCH of a received D2D transmission and may apply thisvalue if it is lower than the current persistence parameter value. Thevalue may be maintained until a timer started upon reception of thetransmission expires.

The persistence parameter may be constrained to be within a definedrange. For example, the persistence parameter cannot decrease below acertain value (or increase above a certain value) even if one of theabove conditions is satisfied.

Supporting parameters may be configured by higher layers, pre-defined,or pre-configured. Supporting parameters may for instance include atleast one of a step size, interval, duration of evaluation period,persistency value (e.g., for one or more, or each, value of a receivedfield if applicable), corresponding interval of the number of receivedtransmission within an evaluation period, or minimum and maximum values.

Properties of received D2D signals as described herein may determine theselection of a resource pool among a set of candidate resources (e.g.,this may be in addition to the persistence parameters). For example, aWTRU may select a resource pool that maximizes (or minimizes) a certainmetric, where the metric may be a function of received D2Dtransmission(s) on the resource pool. The metric may be adjusted as forthe persistence value as described herein (e.g. decrease when the numberof received D2D transmissions in a period of time is higher).

Priority based access may include persistent radio resources.

Priority based access for D2D communications may be realized throughpersistent radio resource allocation to high priority D2D channels orsignals or users.

Persistent radio resource allocation may mean the use of radio resourcetransmission opportunities that may be kept by the D2D terminal for theduration of a high priority D2D transmission and/or for a pre-determinedand/or for a pre-configured duration, such as in excess of a singlescheduling period. A persistent radio resource allocation may becharacterized by that a D2D terminal may keep the acquired radioresources for a prolonged period of time, for example, withoutre-selecting a D2D transmission opportunity, such as when it determinesaccess to D2D radio resources through a channel selection mechanism tostart its high priority D2D channel and/or signal transmission. Channelselection mechanism may, for example, mean random selection of a radioresource, such as a subframe and RB combination. Channel selectionmechanism may mean measurement based radio resource selection, such as aset of least interfered RB's in a subframe. Channel selection may meanresource allocation through another device, such as an eNB.

A D2D terminal intending to transmit a high priority D2D voice groupchannel may determine allowed D2D subframes, for example, frompre-stored information in the device. The pre-stored information mayinclude a set of subframes (e.g., first set of subframes) allowed fortransmission of SA and/or a subframe (e.g., second subframe) set allowedfor use with D2D data over a given transmission period. The D2D terminalmay perform channel selection through measurements on SA subframes todetermine a suitable, least interfered, transmission opportunity for itsSA. The device may select one or more (e.g., two) PRBs in an SA subframefor transmission of its own SA. Channel selection through measurementsto determine least interfered resources may imply deferral oftransmission to a later time instant, such as when the D2D terminalmight not identify a suitable (e.g., not interfered) transmissionopportunity. The D2D terminal may transmit D2D data associated with thisSA over the corresponding scheduling period, for example, once the D2Dterminal starts transmitting the SA. The location of corresponding D2Ddata in subframes and RBs included within the subframes part of thescheduling period may be indicated through a radio resource transmissionpattern (RRTP). The RRTP may be included in the SA, for example, as partof its payload, or it may be given through the time/frequency locationof the SA, or a combination thereof. The D2D terminal may be allowed tokeep the radio resources it acquired (e.g., as opposed to relinquishthese resources) to re-perform channel selection on SA and/or thecorresponding D2D data resources, for example, once the schedulingperiod is over. The D2D terminal may avoid the channel selection and/orany ongoing high-priority D2D transmission might not be interrupted.Priority based access may be improved (e.g., statistically) such thathigh-priority D2D channels might not contend for access to resources.High-priority D2D channels may contend for resources at the beginning ofa transmission. Long (e.g., sufficiently long) high-priority D2Dtransmissions, such as in the order of more than several schedulingperiods, may utilize guaranteed access to D2D radio resources, forexample, once acquired. High-priority D2D data transmissions mayimprove, for example, in that they might not suffer from interruptionduring an ongoing transmission due to channel selection.

A D2D terminal that selected a D2D transmission opportunity in a timeperiod (e.g., first time period) may keep the acquired radio resourcesin a time period (e.g., second time period), for example, if it may havehigh priority D2D data to transmit.

For example, a D2D terminal may have selected to transmit the SA in RBs3-4 of subframe 1 in SFN 1. Transmitting associated D2D data in selectedsubframes from SFN 1-16 may keep using that same or similar SAtransmission opportunity, such as in RB's 3-4 of SFN 17 for the nextscheduling period.

The examples described herein may be extended to fit the purposes ofparticular D2D data characteristics. For example, the RRPT of atransmission period (e.g., first transmission period) may determine theRRPT of a subsequent transmission period. The persistent use of D2Dtransmission opportunities may be indicated by the D2D terminal, forexample, as part of its D2D data and/or control signaling. Such anindication may be realized through part of a payload, such as given byan SA information field, or through the choice of sequence encodingparameters or initialization values or settings, or through of aparticular signaling format in one or more or all of the transmissionperiods.

A D2D terminal that may have selected a D2D transmission opportunity attime instant T1 may keep selected D2D radio resources for apre-determined amount of time before re-selecting a D2D transmissionopportunity.

For example, a D2D terminal having selected to transmit the SA in RBs3-4 of subframe 1 in SFN 1 may keep the radio resources for duration 3.2sec.

D2D service access classes may be described herein.

D2D terminals may store as part of their D2D related configuration theD2D service access class information related to D2D data types they maysupport.

D2D access class information may correspond to any type of parameterused to support priority based access for D2D data transmissions. A D2Daccess class for a given terminal may correspond to those D2D and/orpublic-safety services it may support.

A D2D terminal may (e.g., may only) support file upload and/or download.A D2D terminal might not support public safety voice call groups, suchas it might not support audio applications. The D2D terminal may (e.g.,may only) support an exemplary D2D service access class three and use(e.g., only use) any advertised low-priority D2D access opportunities.

A D2D terminal may support public safety voice groups and/or file uploador download. The D2D terminal may support an exemplary D2D serviceaccess class two and/or three and/or may use high priority and/or lowpriority D2D data access opportunities.

A D2D terminal may support voice (e.g., only voice) and may be reservedfor use by personal in the line of command or for voice call groups. TheD2D terminal may support a (e.g., exemplary) D2D service access classone for highest, emergency-type, voice calls, and/or class two for highpriority D2D data access opportunities.

D2D service access classes may be associated with stored configurationinformation that may establish different types of allowed D2D servicesin D2D terminals.

D2D service access classes stored in a D2D terminal may be used inconjunction with channel access parameters obtained from signaling todetermine allowed D2D time/frequency radio resources by that D2Dterminal. For example, a D2D terminal supporting high priority and lowpriority D2D data transmissions according to its stored D2D serviceaccess class 2 and 3 may read D2D related configuration information froma DL broadcast channel, it may configure its transmitter as a functionof decoded signaling parameters (e.g., as described herein) for theseclasses, and it may discard and/or disregard any information obtainedaccording to advertised D2D service class 1 of highest priority which itmight not support.

D2D service access classes in a D2D terminal may be associated with aset of stored channel access parameters for D2D prioritized access.

For example, a set of allowed D2D subframes (e.g., first set of allowedD2D subframes) for SA transmissions in time may be associated with a D2Dservice access class, for example, in the form of a database or indextable entry. A set of persistence parameters (e.g., first set ofpersistence parameters) may be stored in a D2D terminal associated witha D2D service class (e.g., first D2D service class), such as publicsafety voice. A set of persistence parameters (e.g., second set ofpersistence parameters) associated with a D2D service class (e.g.,second D2D service class), such as file upload or download, may bestored in a D2D terminal.

D2D transmission and/or reception may be disclosed. D2D transmissionand/or reception may include priority handling.

A WTRU may transmit an indication that access to at least one resourceis desired for transmission of certain voice or data traffic. Suchindication may be referred to as desired access indication as describedherein. Such indication may be provided via the use of a pre-emptionindication as described herein. A WTRU receiving such an indication mayinterrupt on-going transmissions and/or refrain from accessing aresource for a period of time. The received indication may be providedto higher layers (e.g., an application layer). This may indicate to theend-user that another user desires access to a resource.

One or more triggers for transmission of a desired access indication maybe provided. A WTRU may initiate transmission of the desired accessindication based on one or more of the following.

An application may request a triggering transmission of the desiredaccess indication. Such request may originate from an end-user, e.g.,through a user interface. For example, one or more of the following mayapply. An end-user may press a specific key or button of the equipmentused for voice or data transmission, for instance in an emergencysituation. The transmission of the Desired Access Indication may betriggered by a speech emotion recognition application detecting anemotion consistent with an emergency situation. Transmission of thedesired access indication may be triggered if the WTRU determines thatone or more available resources (e.g., all available resources) areutilized for transmission from other WTRUs. The indication may betriggered if (e.g., only if) the detected transmissions from other WTRUsare at a lower priority level.

Transmission of the desired access indication may be triggered if (e.g.,only if) the WTRU determines that no other WTRU may have transmitted adesired access indication that may still be valid. If a priority levelis indicated as part of the desired access indication, such conditionmay apply if (e.g., only if) the indication that may be transmitted byanother WTRU indicates priority (e.g., higher or equal priority) thanthe indication to be triggered. Possible conditions to determine if areceived indication is valid may be described herein.

A desired access indication may include one or more of the following.The WTRU may include one or more (e.g., at least one) of the followingas part of the message containing the Indication. An identity of theWTRU. A value identifying traffic that may be concerned by one or moreIndications (“Traffic identity”). For the transmitted Indication (e.g.,first transmitted Indication) related to a given traffic, such value maybe selected (e.g., randomly selected) from the subset of possible valuesthat might not be used by other Indications. For Indications (e.g.,subsequent Indications), the value may be set to the same or similarvalue as in other Indications (e.g., previous Indications) related tothe same or similar concerned traffic. One or more (e.g., at least one)property of the traffic concerned by the Indication, such as: a prioritylevel; a duration; an expected duration; an amount of data; a data rate;a transmission power level; an application; a service. One or more(e.g., at least one) identifier of a resource for which the Indicationmay apply. The WTRU may set the one or more (e.g., at least one)identifier to identify resource(s) concerned by the indication. A periodof time (e.g., or delay) before the concerned traffic may start to betransmitted, and/or before the Indication may be retransmitted. Thisvalue may correspond to the duration of a Wait timer. An indicationwhether, for example at expiry of the delay, the concerned traffic maystart to be transmitted or the Indication may be retransmitted.

Transmission of desired access indication may be described herein. Thedesired access indication may be encoded and/or transmitted over aphysical channel used for control purposes, such as the PD2DSCH. Theindication may be transmitted using the same or similar type oftransport or physical channel as normal traffic, for example, possiblyusing a specific resource or one or more of a set of reserved resourcesfor the indication. The indication may be included as part of aScheduling Assignment and/or may be transmitted within a set ofresources used for the transmission of Scheduling Assignment. Theindication may be transmitted in multiple instances for addedrobustness.

Actions may be taken upon transmission of a desired access indication.Upon transmission of the indication and/or after completingtransmission(s) of the Indication, the WTRU may start a timer (e.g.,referred to herein as the “Wait Timer”) whose duration may correspond tothe (e.g., latest) time at which the WTRU may initiate transmission ofthe concerned traffic and/or may retransmit the Indication. The WTRU maymonitor one or more (e.g., at least one) valid resource to detectwhether it is available and/or if one or more (e.g., at least one) otherWTRUs may be transmitting on the resource. A valid resource maycorrespond to one or more (e.g., one) of a set of resources configuredto be available for transmission of traffic that may be concerned by adesired access indication. The WTRU may (e.g., may only) consider aresource valid if it may be associated with a priority level equal to orlower than the priority level of the concerned traffic.

The WTRU may stop the Wait timer, for example, upon detecting that oneor more (e.g., at least one) resource may be available for transmissionof the concerned traffic. The WTRU may initiate transmission of theconcerned traffic on the one or more (e.g., at least one) resource.

Upon expiry of the Wait timer, the WTRU may perform one or more (e.g.,at least one) of the following actions. The WTRU may re-initiatetransmission of the Indication and/or restart the Wait Timer. The WTRUmay initiate transmission of the concerned traffic on a valid resource,if the WTRU detected or did not detect transmissions from other WTRUs onthis resource. Upon initiation of transmission of the concerned traffic,the WTRU may start a timer (referred to herein as the “Keep-alive”timer).

Upon selection of a resource for transmitting the concerned traffic, theWTRU may initiate transmission of a Selected Resource Indication, forexample, for the purpose of indicating to other WTRUs which resource(s)has been selected. This may allow other WTRUs to resume transmissions onresources not used by the WTRU. The Selected Resource Indication maycontain one or more (e.g., at least one) resource identifier (e.g.,index) and/or a duration or minimum duration for the use of theresource(s). The Selected Resource Indication may be identical orsimilar to a Desired Resource Indication, for example, with signaledvalue(s) for the resource identifier that may be different from atransmitted (e.g., previously transmitted) Desired Resource Indication.

The WTRU may initiate transmission of a subsequent Desired AccessIndication and/or of a Selected Resource Indication, for example, uponexpiry of the Keep-alive timer, if it determines that there may still betraffic concerned by a Desired Access Indication that may betransmitted. The Keep-alive timer may correspond to the same or similarvalue as the Wait timer or be identical or similar to the Wait timer.

The Release Indication may be transmitted. Release indicationtransmission may be disclosed herein. The WTRU may trigger transmissionof a Release Indication and/or stop a Keep-alive timer, for example,when there may be no more traffic concerned by a transmitted (e.g.,previously transmitted) Desired Access Indication that may betransmitted. Such determination may be performed using mechanismssimilar to mechanisms described herein that may be used for triggeringthe Desired Access Indication based on higher layers. A maximum durationfor transmitting traffic concerned by a Desired Access Indication may beconfigured by higher layers or otherwise. The Release Indication mayinclude a Traffic identity corresponding to the concerned traffic. TheRelease Indication may be encoded and/or transmitted over the samephysical channel as the Desired Access Indication.

Actions may be taken upon reception of Desired Access Indication and/orSelected Resource Indication. A WTRU may monitor one or more (e.g., atleast one) physical channel on which other WTRUs may transmit DesiredAccess Indications, Selected Resource Indications and/or ReleaseIndications.

Upon reception of a Desired Access Indication, a WTRU may perform one ormore (e.g., at least one) of the following actions. The WTRU may takethe Indication into account (e.g., only) for traffic that may havepriority lower than or equal to the priority level signaled by thereceived Indication. This may be referred to herein as “de-prioritizedtraffic”. The WTRU may stop a running Wait timer and/or Keep-alive timerassociated to a received (e.g., previously received) Indication, forexample, including the same or similar Traffic identity parameter. TheWTRU may start or may restart a Wait timer with a duration whose valuemay be included in the received Indication.

Upon reception of a Selected Resource Indication, a WTRU may stop arunning Wait timer and/or Keep-alive timer associated to a receivedindication (e.g., previously received indication), for example,including the same or similar Traffic identity parameter, and may startor may restart a Keep-alive timer with a duration whose value may beincluded in the received Indication. The Indication may be sent tohigher layers, such as an application layer or a user interface, forexample, to notify the end user that another user may be attempting toaccess resources. Such notification may be visual (e.g. lightindicator), audible, or tactile (e.g. vibration).

The WTRU may determine whether it is transmitting (e.g., currentlytransmitting) de-prioritized traffic on one or more (e.g., at least one)resource concerned by the Indication. The set of resources concerned bythe Indication may correspond to the one or more (e.g., at least one)value included in the Indication, if present. The set of resources maycorrespond to resources associated with priority levels that may beequal to, or lower than, the priority level included in the Indication.The WTRU may stop (e.g., immediately stop) transmission ofde-prioritized traffic on such resource. The WTRU may stop transmission,for example, at the beginning of the next scheduling period, and/or atexpiry of the Wait timer. Interruption of traffic transmission on aresource may take place if (e.g., only if) another resource may beavailable or if the Indication might not be sent to an application layeror user interface.

While a Wait timer or Keep-alive timer associated to a received (e.g.,previously received) Indication may be running or upon reception of aSelected Resource Indication, a WTRU may select one or more (e.g., atleast one) resource that might not be part of the set of resourcesconcerned by the Indication for transmitting de-prioritized trafficand/or for initiating transmission of de-prioritized traffic.

Actions may be taken upon reception of Release Indication and/or uponexpiry of Keep-alive timer. Upon reception of a Release Indication, theWTRU may stop any timer (e.g., Wait timer or Keep-alive timer)associated to a received (e.g., previously received) Indication, forexample, including the same or similar Traffic identity parameter. TheWTRU may determine that no traffic may be de-prioritized, for example,with respect to the Traffic identity that may be included in the ReleaseIndication. Upon expiry of a Keep-alive timer, the WTRU may determinethat no traffic may be de-prioritized, for example, with respect to theTraffic identity that may be included in the associated ReleaseIndication (e.g., upon reception of which the timer may have beenstarted).

Pre-emption may utilize D2D prioritized channel access.

Pre-emption Indication may be explicit. Explicit pre-emption indicationsand physical processing of a pre-emption indication may be describedherein. In a distributed scheduling D2D system, there may be nocontrolling entity to ensure that high-priority messages get access tothe resources on time. Pre-emption may be a mechanism that may be usedby a device to interrupt (e.g., temporarily interrupt) an on-goingcommunication from another device, for example, so that the resource maybe freed for its own use.

Pre-emption may be motivated, for example, where the resource may beconstrained, such as when a WTRU may transmit a high-priority messageand/or one or more, or each, resource may be utilized (e.g., currentlyutilized). Pre-emption may be used when resources for a group of users(e.g., or other classification) may be occupied and/or a higher prioritysignal for that group may be transmitted (e.g., there are other radioresources available and they may be reserved for other user groups).

A D2D WTRU may be configured to transmit a pre-emption indication. Theindication may consist of a message and/or may carry an amount ofinformation. The indication may consist of a signal, for example, fromwhich an amount (e.g., limited amount) of information may be inferred.

Message-based indication may be described herein. The D2D WTRU may beconfigured to transmit a message-based pre-emption indication. Thepre-emption message may carry one or more of the following information,in any order or combination: a resource index, an identity, a prioritylevel, an amount of time to backoff an interruption cause, and/or T-RPT.The pre-empting WTRU may indicate a specific resource index, for examplethat may be chosen from a list of resources used (e.g., currently beingused). The transmission associated to that resource may be interrupted,regardless of the identity of the user transmitting (e.g., currentlytransmitting) over the resource. The identity may be used to indicate atarget WTRU identity and/or group identity to pre-empt (e.g., whichuser/target group may stop transmission). The priority level may beassociated to the pre-emption message and/or of the data transmission.The WTRU may indicate the priority level associated to its transmission,for example so that WTRUs with lower priority may stop transmission. Theamount of time a pre-empted WTRU may interrupt its transmission. Afterthe backoff time has expired, the pre-empted WTRU may be allowed toresume transmission. The interruption cause may be the cause of thepre-emption. For example, the cause may be chosen from a finite list,including for example, an emergency call, relaying, etc. The T-RPT maybe the pattern index to pre-empt. The WTRU may indicate (e.g.,explicitly) the resources it may want to interrupt.

The WTRU may be configured to transmit the pre-emption message via ascheduling assignment (SA). The WTRU may be configured to use a specialidentifier in the SA to indicate that the SA may be associated to apre-emption message. The WTRU may send the pre-emption message via SA asa control signal, for example.

The pre-emption message may be carried in the SA directly, therebyreplacing the existing fields of the SA. The WTRU may use a reserve SApool to transmit pre-emption message using SA format. The D2D WTRUstransmitting data may be configured to monitor the pre-emption resourcepool to determine whether or not their transmission may be pre-empted.The WTRU receiving the pre-emption message may be configured todetermine (e.g., blindly determine) if a received SA may be aconventional SA or a pre-emption message. The WTRU may make thisdetermination, for example, based (e.g., blindly based) on the CRCappended to the SA and/or pre-emption message. The pre-emption messagepart may be carried in the data associated to the SA. For example, thepre-emption message may be carried via a MAC control element (CE).

The WTRU may be configured to transmit the pre-emption message over aPUCCH resource.

This PUCCH resource may be associated to a D2D transmission. Theassociation may be done, for example, based on the characteristics ofthe SA associated to the transmission that the WTRU may want tointerrupt. For example, the WTRU may be configured to transmit thepre-emption indication at a known instant of time, for example, afterthe SA was transmitted, and/or at a specific PUCCH location infrequency, for example, based on the SA resource that may be used.

The WTRU may use a signal format to transmit the pre-emption message.The WTRU may be configured to transmit the pre-emption message in atime/frequency resource that may be reserved for pre-emption.

The WTRU may be configured to transmit and/or receive a pre-emptionmessage in (e.g., only in) a set of designated time/frequency resources.

The set of designated time/frequency resources for transmission and/orreception of the pre-emption message may be obtained from one or more ofthe following: timing values such as frame or subframe counters;cell-wide or D2D system frame values; timing offset value(s) applied toa reference subframe or frame; offset applied to occurrence(s) of aselected cell-wide or D2D signal or channel; frequency indices, RBs, orgroup of frequency regions; cell-wide or D2D system or WTRU identifier;group communication identifier; or channel or group index value(s).

Some or all parameters may be pre-configured in the WTRU, or they may beobtained through configuration signaling during system operation, orthey may be derived by the WTRU by means of a lookup table or formula orequivalent.

The WTRU may transmit or receive a pre-emption message in a set ofselected and/or reserved subframes that may comprise a subset ofpossible SA subframes. For example, when SA is configured for ascheduling period of 80 ms, then every 4th occurrence of the SAsubframes for a particular Scheduling Period may include pre-emptionmessages. In this case of shared resources where both SA and pre-emptionmessages may be present, the WTRU may distinguish through decodingwhether a particular time/frequency resource includes an SA or apre-emption message.

The WTRU may be configured with a set of D2D subframes not used for SAor D2D data which it may use to transmit and/or receive a pre-emptionmessage. For example when SA is configured for a scheduling period of 40ms, a pre-emption message may be transmitted or received in a designatedD2D subframe reserved for that purpose every 80 ms and which, forexample, otherwise might not be used for SA or data transmissions. Forthis case where dedicated time/frequency resources are used forpre-emption messages, the WTRU may detect a single transmission format(e.g., only need to detect a single transmission format).

The WTRU may transmit and/or receive a pre-emption message in a subsetof D2D data subframes. While SA announces D2D data for a schedulingperiod, a set of D2D data subframes may include control signalingcarrying a pre-emption message. The WTRU may determine presence and/orabsence of a pre-emption message on a set of D2D subframes by means ofdecoding the selected signaling format.

The WTRU may transmit or receive a pre-emption message in one or morelimited frequency regions, which may be selected from a set of possibleD2D subframes in use for control or data. The WTRU may decode forpresence of a pre-emption message or transmit a pre-emption message on(e.g., only on) a selected set of RB's (e.g., 1-10) in a subframeconfigured for SA. Allowed sets of RBs may be known to the WTRU and/orderived from RB indices.

Signal-based indication may be described herein.

The WTRU may be configured to send a signal, for example, as a means forpre-emption indication. This signal may consist of a signal taken from apre-defined list of sequences, for example, based on Zadoff-Chusequences.

While the pre-emption signal itself might not carry any information(e.g., explicit information). Indications (e.g., implicit indications)may be inferred by the receiving WTRU from reception of the signal.

A receiving WTRU may determine information from the pre-emption signal,for example, based on the index of the signal, the time/frequencytransmission and/or others. The pre-emption signal may be transmitted ona set of PRBs that may be associated using a known set of rules to anongoing transmission to pre-empt. The WTRU may be configured to transmitthe pre-emption signal on a set of PRBs associated to the SA associatedto the transmission that it may want to pre-empt.

The WTRU may be configured to select the pre-emption signal (e.g., orthe parameters for generation of the sequence) from a pre-defined list,for example, based on one or more of the following: priority level oftransmission; WTRU Identifier (e.g., RNTI, IMSI, or other); groupcommunication identifier; transmission pattern index, that may be thetransmission pattern associated to the transmission the WTRU desires topre-empt

The WTRU may base the selection of the pre-emption signal on one or moreof the elements described herein.

When to transmit a pre-emption indication may be determined. The WTRUmay be configured to determine conditions when to transmit a pre-emptionindication. The WTRU may be configured to determine to transmit apre-emption indication, for example, based on one or more of thefollowing triggers (in any order or combination). The WTRU may have datato transmit. The WTRU may be configured and/or allowed to usepre-emption. The data to transmit may be associated to a logicalchannel/bearer/QoS/QCI for which pre-emption may be allowed and/orconfigured. The WTRU may receive commands to start/stop pre-emption fromthe higher layers (for example, RRC). The data packet to be transmittedmay be associated with a request for pre-emption sent by higher layers(for example, MAC). The WTRU may have determined, for example, based onmeasurements or monitoring of the SAs, that there may be no radioresources available for transmission of its data. The WTRU may havedetermined that there is one or more (e.g., at least one) resource thatmay be (e.g., currently) used and/or that may be pre-empted. The WTRUmay be configured to determine the priority level of one or more, oreach, data transmission, for example, based on the SA it may receive.The WTRU may be configured to determine for one or more, or each,received SA and/or for one or more, or each, transmission receivedwhether or not it may be pre-empted. This may be carried out, forexample, based on one or more of the absolute priorities, the identityof the transmission sources, the target identity for transmission, etc.For example, the priority of the data to transmit may be higher than oneor more (e.g., at least one) on-going transmission. The priority of theWTRU may be higher than the priority of one or more (e.g., at least one)other WTRU transmitting data. The priority of the target group may behigher than the priority of one or more (e.g., at least one) othertarget group for which data may be being transmitted to.

A WTRU may take actions upon reception of a pre-emption indication. AD2D WTRU transmitting data may be configured to monitor for potentialpre-emption indications. The WTRU may be configured to receive thepre-emption indication in a reserved known time/frequency locationand/or may be configured to receive the pre-emption in an SA.

The WTRU may determine whether or not to act on the received pre-emptionsignal.

When a WTRU may determine that it has received a pre-emption indication,the WTRU may be configured to determine if it may act and/or may wish toact on the pre-emption indication. The WTRU may be configured todetermine whether or not it may act and/or may wish to act on thereceived pre-emption indication, for example, based on one or more ofthe following. The priority level that may be associated to thepre-emption indication (e.g. explicit pre-emption priority level,priority level associated to the transmitter of the pre-emptionindication, priority level of the target group, etc.). The target WTRUthat may be associated to the pre-emption indication. For example, thepre-emption indication may carry information to indicate a targettransmitter/transmission to interrupt. The WTRU may be configured todetermine if it is the target of the pre-emption indication, forexample, based on the content of the pre-emption message (e.g.transmitter identifier, group identifier, specific resource identifier,priority level, etc.), or (e.g., implicitly) based on thetime/frequency/signal characteristics of the pre-emption signal.

Pre-emption application may be described herein.

The WTRU may act on the pre-emption indication received by the WTRU andmay be configured to release the resource that may be pre-empted. TheWTRU may be configured to perform the following, for example, upondetection of a pre-emption indication for which it may determine that itmay act upon and/or may wish to act upon. The WTRU may stop datatransmission. The WTRU may release the resource. The WTRU may beconfigured to stop transmission of the SA. The WTRU may be configured totransmit an indication of a resource release. For example, the WTRU maybe configured to transmit a special indication in an SA to indicatetermination, indicating (e.g., optionally indicating) the cause of thetransmission termination (e.g., pre-emption). The WTRU may be configuredto start a backoff timer (e.g., of a pre-defined value). The WTRU mightnot be allowed to resume data transmission and/or attempt transmissionof data, for example, until the timer expires. Once the pre-emption maybe completed and/or a pre-emption timer has expired, the WTRU may beconfigured to re-initialize transmission as if it was a new (e.g. freshor updated) transmission (e.g., re-evaluating the transmissionparameters).

The WTRU may be configured to “keep” the resource for the duration ofthe pre-emption interruption. The WTRU may be configured to transmit anindication to keep the resource. For example, the WTRU may be configuredto transmit an indication in an SA to indicate resource reservation(e.g. “channel hold”), indicating (e.g., optionally indicating) thecause of the resource reservation (e.g., pre-emption). The WTRU may beconfigured to start a backoff timer (e.g., of a pre-defined value). TheWTRU might not be allowed to resume data transmission and/or attempttransmission of data until the timer expires. Once the pre-emptionprocedure is completed and/or a pre-emption timer has expired, the WTRUmay be configured to resume transmission using the same resource thatwas pre-empted. The WTRU may be configured (e.g., optionally beconfigured) to resume (e.g., only resume) transmission using the same orsimilar resource, for example, if it resumes transmission within thesame or similar scheduling period. The WTRU may be configured toindicate to the higher layers reception of a pre-emption indication thatit may act upon and/or may wish to act upon. For example, the WTRU maybe configured to indicate to the higher layers when the channel may bebusy and/or the WTRU may be holding transmission. The WTRU may beconfigured to indicate to the higher layers when it may fail to transmitdata due to pre-emption. This may be relevant for delay-sensitiveapplications for which the data may be discarded after some time haselapsed. The WTRU may indicate to higher layers when the duration of theinterruption due to pre-emption may be longer than a specificpre-defined duration.

D2D terminals may be utilized to implement prioritized channel access.

Transmit and/or receive half-duplex may be utilized priority basedaccess. D2D terminals may process multiple D2D channels/signals to betransmitted and/or to be received based on priority of the D2D channeland/or signals.

A receiving D2D terminal may have multiple concurrent D2D channelsand/or signals to receive and/or to transmit. Based on the priority forthese D2D channels or signals, it may adjust it reception and/ortransmission schedule to allow for prioritized reception (e.g., ortransmission) of a high priority D2D channel/signal.

FIG. 9 is an example diagram of prioritized reception of a high-prioritychannel by D2D terminal with FDD half-duplex operation. In FIG. 9 , aD2D terminal (e.g., concurrently) may have a high priority D2D voicechannel (e.g., first high priority D2D voice channel) to receive, suchas for a voice group call, while it may have a lower priority D2D datachannel (e.g., second lower priority D2D data channel), such as for fileupload to transmit.

In FIG. 9 , a talk spurt corresponding to the incoming high priority D2Dvoice channel may be received over multiple scheduling periods, forexample, until time instant T2. A device internal request to transmit alow priority D2D data channel (e.g., second low priority D2D datachannel) may be received, for example, beginning from time instant T1.The request may be issued by the user or by an application that mayprocess data packets for D2D and may emit such a request. The D2Dterminal may have a Tx/Rx front-end operating under half-duplexconstraints for D2D channels and/or signals on the cellular ULfrequency, for example in any subframe it may transmit a D2D channeland/or signal, or it may receive a D2D channel and/or signal. The D2Dterminal may be able to receive multiple D2D channels and/or signals(e.g., simultaneously) in the same or similar subframes.

Upon arrival of the transmission request for the low priority D2D datachannel (e.g., second low priority D2D data channel) at time instant T1,the D2D terminal may adjust its transmission schedule to allow for fullreception of one or more or all subframes corresponding to the highpriority D2D channel. The D2D terminal may choose to not use certainsubframes originally scheduled for transmission of the low priority D2Dchannel and use the indicated subframes for reception of the highpriority D2D data channel, for example, if a collision occurs. At timeinstant T2, when the talk spurt of the incoming high priority D2D voicechannel ends, and the D2D data channel (e.g., only the low priority D2Ddata channel) may be transmitted, the D2D terminal may adjust itstransmission pattern to allow for full transmission of the low priorityD2D data channel (e.g., second low priority D2D data channel). Whileprioritizing reception of the high priority D2D channel during timeperiod T1-T2, the D2D terminal may choose to indicate a radio resourcetransmission pattern (RRPT) that may be chosen as a function of the D2Dsubframes that may be determined available for transmission, forexample, after taking those for reception into account. The D2D terminalmay choose to indicate an RRPT that may include D2D subframes for itsown transmission and/or where it may receive high-priority D2D data. TheD2D terminal might not transmit in these.

A D2D terminal may process (e.g., automatically process) one or more, ormultiple, D2D channels and/or signals to be transmitted and/or to bereceived based on priority handling associated with such multiple D2Dchannel and/or signals. No user intervention, such as manual channelswitching or deferral of transmission, may be utilized. Signal receptionfor high-priority D2D channels may be received by dedicating receptioncapabilities (e.g., full reception capabilities) to D2D subframescarrying that high priority D2D channel and/or signal.

In some techniques described herein, the SA resources for high prioritytransmissions by one or more, or a given, WTRU may be configured tooccur earlier in time than, the SA resources for low prioritytransmissions, perhaps for the same SA period, for example. This can beconfigured by the eNB, for example, by assigning them to different SAresource pools. The WTRU with low priority transmissions may decode thehigh priority SA resources to determine whether higher priority data maybe received (e.g., first). Perhaps for example, based on thisdetermination, among other scenarios, the WTRU may decide to nottransmit on the configured low-priority SA resources, or the WTRU maytransmit on the configured low-priority SA resources. The WTRU mayindicate an RRPT which may allow it to receive the high prioritytransmission while transmitting (e.g., perhaps for example despite thehalf-duplex arrangement in some embodiments).

The examples described herein may be extended to more than two priorityclasses. Different lengths of scheduling periods may be used. SAtransmissions may correspond to D2D data transmitted in a later and/orin multiple scheduling periods. Independently or in conjunction withscheduling periods, principles of semi-persistent, time-limited ordynamically granted D2D data transmissions may be used. Time and/orfrequency resources might not be contiguous. While the examples usedscheduling assignments and/or high and low priority received D2D voiceand data channels for illustration purposes, the principle of allocatingtransmission and reception subframes corresponding to a low or to highpriority D2D channels or signals may equally be applied to different D2Dchannel and/or signal messages types. For example, D2D discoverymessages may be skipped for transmission and/or deferred to later forprocessing, while a high priority D2D control or data signaling may bereceived. The principle of Rx prioritization may be applied to theopposite case where D2D subframes may be prioritized for transmission,such as a high priority D2D channel signal may be transmitted by the D2Dterminal, while a low priority D2D channel and/or signal may bereceived.

Received (e.g., concurrently received) D2D data may be voice, control,service and/or data packets, such as for IP packets corresponding to afile download. Tx/Rx processing and/or prioritization of multiplechannels and/or signals to be received or to be transmitted may equallybe applied to channels and/or signals received or transmitted on thecellular communications and the D2D radio links.

A D2D terminal while receiving or transmitting a D2D channel and/orsignal (e.g., first D2D channel and/or signal) may determine whether aD2D channel and/or signal (e.g., second D2D channel and/or signal) maybe transmitted or received. Upon determination that a D2D channel and/orsignal (e.g., second D2D channel and/or signal) may be present, the D2Dterminals may determine which of the D2D channels or signals that may betransmitted or received has higher priority. The determination may bebased on priorities associated with D2D channels or signals orcommunication types. The WTRU may determine the priority of the receivedchannel and/or signal based on a priority of the pool or channel,time/frequency, etc., in which the data and/or SA was received; this maybe based on an explicit indication in the SA, based on a MAC headerindication, or based on any of the features described herein.

A D2D terminal may determine a transmission and/or reception schedule toallow for a suitable number of D2D subframes to be used for transmissionor reception of the high priority D2D channel and/or signal. A D2Dterminal may determine suitable D2D subframes based on a variety ofcriteria, such as one or more of: a minimum and/or identified set of SAresources in order to be able to receive or transmit SAs, a requirednumber and/or set of D2D subframes corresponding to possible D2D Datareception or transmission, a number of set of subframes not availablefor the purpose of D2D transmission and/or reception due to ongoingcellular communication, and/or a number and/or set of D2D subframescorresponding to transmission and/or reception from/to one or more WTRUsand/or D2D communication group(s).

The D2D terminal may determine to skip transmission or receptionopportunities originally planned for the low priority D2D channel and/orsignal. The D2D terminal may select available transmission/receptionopportunities for transmission and/or reception of the lower priorityD2D channel and/or signal by determining which transmission/receptionopportunities may be used for the high priority D2D channel and/orsignal. The WTRU may continue with the transmission or reception of thelower priority D2D channel or D2D signal, but may skip the transmissionor reception in the subframes overlapping with the subframes in whichreception or transmission of the higher priority D2D channel or D2Dsignal is taking place.

The D2D terminal may, in conjunction with examples described herein,issue notifications and/or signaling messages exchanged from or to orin-between a device component and another to announce or inform aboutactions that may be undertaken as part of its receiver processing. Itmay issue such notifications or signaling messages to other devices. TheD2D terminal may be configured to perform the examples described herein,for example, as a function of selected reception conditions, receiverconfigurations, timers or counters or index values.

A D2D terminal may process multiple D2D channels and/or signals to betransmitted or received, for example, based on priority associated withthese D2D channels or signals. Processing may involve the selection oftransmission and/or reception opportunities of a D2D channel and/orsignal (e.g., first D2D channel and/or signal) as a function of thoseuseful for a D2D channel and/or signal (e.g., second D2D channel and/orsignal).

Reception to process multiple D2D data channels by a device may bedescribed herein.

D2D terminals may process multiple received (e.g., concurrentlyreceived) D2D channels or signals based on priority of the received D2Dchannel and/or signals.

A receiving D2D terminal may receive multiple incoming (e.g., concurrentincoming) D2D channels or signals. Based on the priority for thereceived D2D channels or signals, it may store (e.g., temporarily store)received channel samples, demodulated or decodable bit streams ordecoded information contents that may correspond to a received lowerpriority D2D channel and/or signal in memory, while processing and/orforwarding another higher priority D2D channel and/or signal and/orpresenting it to user or device output.

FIG. 10 is an example diagram of multiple concurrently received D2Dchannels (e.g., voice). In FIG. 10 , a D2D terminal may concurrentlyreceive a D2D voice channel (e.g., first high priority D2D voicechannel), such as for an emergency first responder direct voice lineand/or a D2D voice channel (e.g., second lower priority D2D voicechannel), such as for a push-to-talk group call.

In FIG. 10 , a talk spurt corresponding to the high priority D2D voicechannel (e.g., first high priority D2D voice channel) may be receivedover multiple scheduling periods until time instant T2. A talk spurt ofa low priority D2D voice channel (e.g., second low priority D2D voicechannel) may be received beginning from time instant T1. The D2Dterminal may have one audio processing front-end chain, for example atany given point in time decoded (e.g., only decoded) voice samples ofone channel may be presented to audio output, such as speakers orotherwise, the D2D terminal may process (e.g., only process) onereceived voice channel at a time. The D2D terminal may be able toreceive both the low-priority and/or the high-priority D2D channelsand/or control signaling simultaneously in different subframes or in thesame or similar subframes that may be used to carry D2D channels and/orsignals.

Perhaps upon the start of reception of the low priority D2D voice call(e.g., second low priority D2D voice call in FIG. 10 ) at time instantT1, among other scenarios, the D2D terminal may continue to demodulate,to decode and/or to forward to the audio output path of the device anyD2D data obtained from the high priority voice channel (e.g., first highpriority voice channel in FIG. 10 ) while it may store (e.g.,temporarily store) any decoded samples or signal representations of the(e.g., concurrently) received lower priority D2D voice call (e.g.,second lower priority D2D voice call in FIG. 10 ) into memory. At timeinstant T2, when the talk spurt of the high priority D2D voice channel(e.g., first high priority D2D voice channel in FIG. 10 ) ends and thelow priority D2D voice channel (e.g., only the low priority D2D voicechannel in FIG. 10 ) may be received, the D2D terminal may switch itsaudio path from the high priority D2D voice channel to the low priorityD2D voice channel. Forwarding such stored channel samples and/or decodedinformation contents corresponding to the low priority D2D voice channelfrom the memory (e.g., temporary memory) to the audio path may involve atime delay or time lag. For the example, in FIG. 10 , three schedulingperiods or around 480 ms or 24 voice frames at 20 ms codec intervalseach are processed and replayed from temporary memory. One or more(e.g., many) D2D applications may correspond to push-to-talk type ofvoice rather than bi-directional conversational voice. Such a time-delayor time-lag introduced through storing (e.g., temporarily storing) thelow priority D2D voice channel may be acceptable.

The D2D receiver processing may be improved, for example, in that a D2Dterminal may (e.g., automatically) receive and/or process multiple D2Dchannels or signals (e.g., concurrent D2D channels or signals) based onpriority handling associated with such received multiple D2D channeland/or signals. No user intervention, similar to manual channelswitching, may be useful. Higher priority D2D channels and/or signalsmay be prioritized through D2D terminal processing upon reception, forexample, in the presence of other channels and/or signals.

The WTRU may be configured or pre-configured with rules to determinewhether data of different priority can be multiplexed together in onePDU or whether they may be required to be transmitted in differenttransmission opportunities. For example, the network may allow a WTRU tomultiplex data belonging to a second and third priority level but notdata corresponding to a first priority level. This restriction may bebeneficial, e.g., if the WTRU wants to optimize the transmission ofemergency services without multiplexing data of lower priority in thesame TB.

Examples described herein and FIG. 10 may be extended to more than twopriority classes. Different lengths of scheduling periods may be used.SA transmissions may correspond to D2D data transmitted in a later or inmultiple scheduling periods. Independently or in conjunction withscheduling periods, principles of semi-persistent, time-limited ordynamically granted D2D data transmissions may be used. Time and/orfrequency resources might not be contiguous. While the examples usedscheduling assignments and high and low priority received D2D voicechannels for illustration purposes, the principle of temporarilybuffering and storing of a samples corresponding to a low priority D2Dchannel and/or signal may equally be applied to different D2D channeland/or signal messages types. For example, D2D Discovery messages may be(e.g., temporarily) stored for processing at a later time instant, whilehigh priority D2D control or data signaling may be processed uponreception.

Received D2D data (e.g., concurrently received D2D data) may be voice,control, service and/or data packets, such as for example IP packetscorresponding to a file download. The use of buffering and/or storing(e.g., temporary buffering and/or storing) in memory of samplescorresponding to a received D2D channel (e.g., second received D2Dchannel) may be applied, for example, to avoid receiver limitations in aD2D terminal for device architecture, component availability forreal-time processing, device output representation of received D2D data,and/or required user interaction, etc. Receiver processing and/orprioritization of multiple received (e.g., concurrently received)channels and signals may equally be applied to channels or signalsreceived from the cellular communications and the D2D radio links.

A D2D terminal, while receiving a D2D channel and/or signal (e.g., firstD2D channel and/or signal), may determine whether a D2D channel and/orsignal (e.g., second D2D channel and/or signal) may be received. Upondetermination that a D2D channel and/or signal (e.g., second D2D channeland/or signal) may be received, the D2D terminals may determine whichone of the received (e.g., concurrently received) D2D channels orsignals may be directly processed and/or which one may be stored (e.g.,temporarily stored) in memory. The determination may be based onpriorities associated with received D2D channels or signals orcommunication types. Directly processing any decoded samples of a D2Dchannel and/or signal may imply presenting these samples to user output,such as the terminal's audio path, or it may imply forwarding suchsamples to other processing components implemented on the D2D terminal,such as an application processing data packets. Storing (e.g.,temporarily storing) in memory may be combined with partial receiverprocessing, such as for a channel demodulation of received a D2D channeland/or signal, or a channel decoding technique of demodulated samples,or protocol processing of such samples. A D2D terminal may determinewhen to process any D2D data stored (e.g., temporarily stored) inmemory. The D2D terminal may determine to apply direct processing, forexample, as described herein to the stored (e.g., temporarily stored)samples or information contents of the D2D channel and/or signal. TheD2D terminal may forward the stored samples to output components of thedevice, such as audio or video or to other processing logic orapplications processing received data on the device. It may determinethat stored samples may be discarded, for example, if a time delay or aselected set of conditions may be met. Samples may be stored inpermanent storage, for example, to allow the end-user to listen at alater time.

The D2D terminal, in conjunction with examples described herein, mayissue notifications and/or signaling messages exchanged from or to orin-between a device component and another to announce and/or informabout actions that may be undertaken as part of its receiver processing.It may issue such notifications or signaling messages to other devices.The D2D terminal may be configured to perform examples described hereinas a function of selected reception conditions, receiver configurations,timers or counters or index values.

A D2D terminal may process multiple received D2D channels or signals,for example, based on priority of received (e.g., concurrently received)D2D channels or signals. Processing may involve receiving and/ordiscarding and/or prioritizing for reception a D2D channel and/orsignal, for example, in the presence of other D2D channels or signals.

A D2D terminal may selects a received (e.g., first received) D2D channeland/or signal for direct processing, for example, while selecting areceived (e.g., second received) D2D channel and/or signal for storage(e.g., temporary storage). Direct processing and/or temporary storagemay correspond to the example realizations described herein, for examplewith respect to the example receiver.

One or more techniques are contemplated for reception by a D2D WTRUserving as a Relay Node. A relay WTRU may operate as an L3 relay. Insuch scenarios, among others, data received over the D2D link may beforwarded to one or more upper layers (e.g. IP, among others), perhapsfor example before it may be sent over the Uu interface to an eNB. Arelay WTRU may implement (e.g. particular) handling for priority,perhaps for example when it may receive data (e.g., over the D2D link)and/or may relay this traffic over the cellular link to the network. Theprioritization of data transmitted by a WTRU to the network (e.g., via arelay) may be the same or substantially similar prioritization on theD2D link as the prioritization experienced over the cellular link fromthe relay WTRU to the eNB.

In one or more techniques, the relay node may request and/or create oneor more separate radio bearers for one or more, or each, level ofpriority of data that it may receive, of example from any of the remoteWTRUs it may be currently serving. The relay WTRU may utilize one ormore existing radio bearers that may be associated with (e.g., varying)degrees of Quality of Service (QoS), perhaps for example to serve theone or more different priority transmissions made by the remote WTRUtowards the relay (e.g., with higher priority transmissions being mappedto one or more bearers with better QoS, or the like), among otherscenarios.

A relay WTRU may setup one or more, or a set, of radio bearers for oneor more, or each, of the N priority levels it may be serving, and/or theWTRU may select one or more existing radio bearers that may be used fordata associated with one or more, or each priority level. Perhaps whenthe relay WTRU receives data from the D2D link, for example, among otherscenarios, it may determine the priority of the packet(s) received froma remote WTRU. This determination may be done, for example, at the MAClayer, the IP layer, and/or the application layer, among other layers.For example, if the determination is done at the MAC layer, the prioritylevel of the received MAC PDU can be determined by one or more of:

-   -   Having the transmitter of the MAC PDU include a priority level        in the MAC header. In such scenarios, among others, the        receiving MAC entity may determine the priority based on the        associated priority level found in the MAC hearer for that PDU,        for example; and/or    -   Assuming a static and/or determined mapping between logical        channel IDs and priority. The value of the logical channel ID        may be associated with a specific priority. For instance, LCIDs        1-8 could be utilized for D2D communication, and the priority        level may be associated with the chosen ID (e.g., in        increasing/decreasing order of priority).

The WTRU may send the received data, perhaps along with the associatedpriority level, to one or more higher layers (e.g., an IP layer) forforwarding over the cellular link.

For example, if the priority determination is done at the IP layer,and/or the application layer, the associated priority may be sent withthe IP packet and/or with the associated application layer data, perhapsfor example so that the relay WTRU may be aware of the priority of thereceived data. The data may be (e.g., first) forwarded to the one ormore higher layers where the priority determination may be performed.

Perhaps based on the priority of the received data, for example, therelay WTRU may determine which radio bearer (e.g., with associated QoSlevel) to use for transmission of the received data. The relay WTRU maymaintain a mapping of radio bearer to priority level, and/or may usethis mapping to decide which radio bearer one or more IP packet(s) maybe sent over. The WTRU may be configured (e.g., dynamically) with amapping of priority level to radio bearer by the eNB, and/or may usethis mapping for transmitting one or more IP packets over the one ormore existing radio bearers.

In some techniques, one or more, or multiple, radio bearers with thesame or similar QoS characteristics may be used by the relay WTRU totransmit data received from the remote WTRU to the eNB/network. Therelay WTRU may (e.g., selectively) forward the higher priority data tothe one or more upper layers, perhaps for example while buffering thelower priority data for a certain period of time. The relay WTRU,perhaps when processing one or more, or each, of the logical channelsthat may be used to transmit data that was received from the remoteWTRU, among other scenarios, may process the higher priority (e.g.,forwarded to the higher layers), and/or may process the lower prioritydata perhaps when (e.g., only when) the lower priority data is forwardedto the higher layers.

For example, the relay WTRU may be configured with a timer over whichlower priority data may be buffered, perhaps for example whileforwarding higher priority data. The timer may be reset one or more, oreach time, a higher priority packet is received by the relay WTRU and/orforwarded to the one or more upper layers. Perhaps after (e.g., onlyafter) the timer expires (e.g., which may indicate that no higherpriority data is received for a period of time), among other scenarios,the WTRU may forward any buffered lower priority data to the one or moreupper layers.

For example, the relay WTRU may forward lower priority data for ascheduling period, perhaps for example when (e.g. only when) no higherpriority data has been received for that scheduling period. Perhaps forexample if a given scheduling period in the WTRU experiences thereception of high priority data, one or more, or all, lower prioritydata may be buffered in the one or more lower layers of the relay WTRU,perhaps while the higher priority data (e.g., only the higher prioritydata) may forwarded to the one or more upper layers.

In some techniques, the WTRU may (e.g., selectively) forward data to theupper layers with a particular probability. A higher probability offorwarding may be associated with the higher priority data/channel,and/or a lower probability of forwarding may be associated with thelower priority data/channel. The higher layer may process the data,perhaps for example in the order received.

For example, the relay WTRU receiving data with for example twodifferent priorities (e.g., high and low) may be configured with a firstprobability (P1)=0.8 for higher priority data and/or a secondprobability (P2)=0.2 for lower priority data. Perhaps for example if therelay WTRU, at any time, contains high priority and/or low priority datato be forwarded to the one or more upper layers, the relay WTRU mayselect a random number between 0 and 1. For example, the relay WTRU mayforward the high priority data perhaps if the number is larger than 0.2.Perhaps for example if the number is otherwise, the relay WTRU mayforward the lower priority data.

Although some techniques may have been described herein using twopriority levels, any of the contemplated techniques can be extended tomultiple (N) priority levels by a person skilled in the art.

Transmission to process multiple D2D data channels in a device may bedescribed herein. D2D terminals may process multiple D2D channels orsignals (e.g., concurrent D2D channels or signals) to be transmittedbased on priority of the D2D channels or signals.

A D2D terminal may transmit and/or wish to transmit multiple D2Dchannels or signals (e.g., concurrently). Based on the priority for theD2D channels or signals to be transmitted, it may store (e.g.,temporarily store) information contents or encoded bit streams orsamples corresponding to a lower priority D2D channel and/or signal tobe transmitted in memory, for example, while processing and/orforwarding another higher priority D2D channel and/or signal andpresenting it to the transmit path.

A D2D terminal may transmit and/or wish to transmit a D2D signal when noresource may be available for transmission. It may store (e.g.,temporarily store) information contents or encoded bit streams orsamples of this signal, for example, until a resource may becomeavailable and/or until a timer expires. Upon expiration of the timer,the samples may be discarded or stored in storage (e.g., permanentstorage) to allow the end-user to access the non-transmitted signallater.

FIG. 11 is an example diagram of multiple concurrent D2D channels to betransmitted (e.g., voice and data). In FIG. 11 , a D2D terminal maytransmit (e.g., concurrently transmit) a high priority D2D voice channel(e.g., first high priority D2D voice channel), such as a voice callgroup channel and/or a lower priority D2D channel (e.g., second lowerpriority D2D channel), such as a file upload.

In FIG. 11 , a talk spurt corresponding to the high priority D2D voicechannel (e.g., first high priority D2D voice channel) may be processedby the D2D terminal over multiple scheduling periods, for example, untiltime instant T2. A device internal request to transmit a low priorityD2D data channel (e.g., second low priority D2D data channel) may bereceived, for example, beginning from time instant T1. The request maybe issued by the user or by an application that may process data packetsfor D2D and/or may emit such a request. The D2D terminal may have atransmit (e.g., single transmit) front-end chain. In any given subframe,one or more (e.g., only one) Transport Block (TB) of a D2D channel maybe presented to the Tx path, for example, in order to use its (e.g.,full) available output power on that subframe for the D2D channel underconsideration. This may maximize the achievable link budget for the D2Dchannel. The D2D terminal may be able to transmit the high priorityand/or the low priority D2D channels and/or its control signaling (e.g.,simultaneously control signaling) in different subframes.

Upon arrival of a transmission request for the low priority D2D datachannel (e.g., second low priority D2D data channel) at time instant T1,the D2D terminal may continue to forward to the transmission path anyD2D data that may be available for the high priority voice channel(e.g., first high priority voice channel) while it stores (e.g.,temporarily stores) and/or buffers in memory any samples or signalrepresentations of the to be transmitted (e.g., concurrently to betransmitted) lower priority D2D data channel (e.g., second lowerpriority D2D data channel). At time instant T2, when the talk spurt ofthe high priority D2D voice channel (e.g., first high priority D2D voicechannel) may end and the low priority D2D data channel (e.g., only thelow priority D2D data channel) may be transmitted, the D2D terminal mayswitch its transmission path from the high priority D2D voice channel tothe low priority D2D data channel. Forwarding such stored samples and/orinformation contents corresponding to the low priority D2D data channelfrom the memory (e.g., temporary memory) to the transmission path mayinvolve a time delay or time lag. For example, in FIG. 11 , around threescheduling periods or around 480 ms may be processed from temporarymemory. Given that D2D applications may correspond to non-time criticaldata type, for example rather than bi-directional conversational voice,such a time-delay or time-lag introduced through storing (e.g.,temporarily storing) portions or the entirety of the low priority D2Ddata transmission may be acceptable.

In FIG. 11 , the D2D terminal may multiplex lower priority D2D datatransmissions intermittently, for example, during an ongoing higherpriority D2D voice channel transmission. It may do so in the D2Dsubframes (e.g., only in the D2D subframes in FIG. 11 ) that might notbe used for transmission of transport blocks for the higher priority D2Dvoice channel. By the time instant T2, lower priority D2D data that maybe ready for transmission and received by the transmit path between timeinstants T1 and T2 for the low priority channel may have been sentbetween T1 and T2.

The D2D transmitter processing may be improved in that a D2D terminalmay process (e.g., automatically process) multiple D2D channels orsignals (e.g., concurrent D2D channels or signals) to be transmittedbased on priority handling associated with such multiple D2D channeland/or signals to be transmitted. No user intervention, similar tomanual channel switching or deferral of transmission, may be useful.Higher priority D2D channels and/or signals may be prioritized throughD2D terminal processing upon request to send, for example, in thepresence of other channels or signals.

The examples described herein and as shown in FIG. 11 may be extended tothe cases of more than two priority classes. Different lengths ofscheduling periods may be used SA transmissions may correspond to D2Ddata transmitted in a later or in multiple scheduling periods.Independently and/or in conjunction with scheduling periods, principlesof semi-persistent, time-limited or dynamically granted D2D datatransmissions may be used. Time and/or frequency resources might not becontiguous. The examples may have used scheduling assignments and highand low priority D2D voice and data channels to be transmitted forillustration purposes. The principle of temporarily buffering andstoring of a samples corresponding to a low priority D2D channel and/orsignal to be transmitted may equally be applied to different D2D channeland/or signal messages types. For example, D2D Discovery messages to betransmitted may be stored (e.g., temporarily stored) and/or queued forprocessing at a later time instant, while high priority D2D control ordata signaling may be processed upon reception of a request to send inthe D2D terminal.

D2D data channels or signals (e.g., concurrent D2D data channels orsignals) to be transmitted may be voice, control, service and/or datapackets, such as for example IP packets corresponding to a file upload.The use of buffering and/or storing (e.g., temporary buffering and/orstoring) in memory of samples corresponding to a D2D channel (e.g.,second D2D channel) to be transmitted may be applied to avoidtransmitter limitations in a D2D terminal with respect to devicearchitecture, component availability for real-time processing, deviceoutput representation of D2D data, usage of radio resources, and/orrequired user interaction, etc. Transmitter processing and/orprioritization of multiple channels and/or signals (e.g., concurrentchannels and/or signals) to be transmitted may equally be applied tochannels or signals to be transmitted on the cellular communications andthe D2D radio links.

A D2D terminal, while transmitting a D2D channel and/or signal (e.g.,first D2D channel and/or signal) may determine whether a request to senda D2D channel and/or signal (e.g., second) may be received. Upondetermination that a D2D channel and/or signal (e.g., second D2D channeland/or signal) is to be transmitted, the D2D terminals may determinewhich of the D2D channels or signals (e.g., concurrent D2D channels orsignals) to be transmitted may be directly processed and which may bestored (e.g., temporarily stored) in memory. The determination may bebased on priorities associated with D2D channels or signals orcommunication to be transmitted. Directly processing any samples orinformation representative of a D2D channel and/or signal to betransmitted may imply presenting the information to the terminal'stransmit path, or it may imply forwarding such samples to otherprocessing components implemented on the D2D terminal. Storing (e.g.,temporarily storing) in memory may be combined with partial transmitterprocessing, such as a channel modulation of a D2D channel and/or signalto be transmitted, a channel encoding of information, and/or protocolprocessing of such D2D channels or signals.

A D2D terminal may determine when to process any D2D data stored (e.g.,temporarily stored) in memory. The D2D terminal may determine to applydirect processing, for example as described herein, to such stored(e.g., temporarily stored) samples or information contents of a D2Dchannel and/or signal to be transmitted. The D2D terminal may forwardthe stored samples to output components of the device, such as thetransmitter path. It may determine that stored samples may be discardedif, for example, a time delay and/or a selected set of conditions may bemet. The device may as part of transmitted (e.g., concurrentlytransmitted) portions of the low priority D2D channel and/or signal(e.g., second low priority D2D channel and/or signal), for example,during a time period when it may transmit a higher priority D2D channel,such as in subframes that might not be in use by the higher priority D2Dchannel and/or signal

The D2D terminal may, in conjunction with examples described herein,issue notifications and signaling messages exchanged from or to orin-between one or more (e.g., one) device component and another toannounce and/or inform about actions that may be undertaken as part ofits transmitter processing. It may issue such notifications or signalingmessages to other devices. The D2D terminal may be configured to performexamples described herein as a function of selected conditions,transmitter configurations, timers or counters, and/or index values,etc.

A D2D terminal may process multiple D2D channels or signals to betransmitted based on priority of the concurrent D2D channels or signalsto be transmitted. Processing may involve transmitting and/or discardingand/or prioritizing portions or the entirety of a D2D channel and/orsignal to be transmitted, for example in the presence of other D2Dchannels or signals to be transmitted by the device.

A D2D terminal may select a D2D channel and/or signal (e.g., first D2Dchannel and/or signal) to be transmitted for direct processing, whileselecting a D2D channel and/or signal (e.g., second D2D channel and/orsignal) to be transmitted for storage (e.g., temporary storage). Directprocessing and/or storage (e.g., temporary storage) may correspond tothe example realizations described herein with respect to thetransmitter.

The D2D terminal may transmit D2D data by determining priority accessgroups and/or mapping from available D2D data channels or signals toavailable priorities or priority access groups.

Priority access groups to transmit data may be selected.

The WTRU may be configured with number of discrete priority accessgroups and may have multiple services or application running. The WTRUmay determine how to map D2D data to transmit into the availablepriority access groups.

Priority access group may refer herein to any of the schemes or resourcepool configurations described herein to support data prioritizationand/or traffic differentiation (e.g. different resource pools withdifferent priorities, prioritization access within the same resourcepool, etc.).

The WTRU may determine the priority access group(s) to use based on oneor more or a combination of the following parameters described herein.The WTRU may use a configured mapping between logical channel prioritiesor LCG priorities of ProSe bearers and/or ProSe/application layer packetand/or a priority access group. For example, ProSe bearers configuredwith logical channel priority 1-4 may be mapped to priority access group1 or highest priority group. One or more, or each, service associatedwith a particular group, traffic type, and/or user type may have anassigned priority by higher layers. When the packet arrives to theaccess stratum it may be mapped to a logical channel or PDCP entitybased on the group destination, source destination, and/or associatedpriority. For the given logical channel the WTRU may be aware of thepriority of the packets and based on a mapping the WTRU may determine towhich priority access group the packet or logical channel belongs to.The WTRU may determine the priority access group(s) based on a mappingof a TFT to a priority access group or to a logical channel (or packet)priority. The WTRU may be configured with a set of TFT filters for oneor more, or each, traffic type, and the priority of the logical channelor access group to be associated with one or more, or each, traffictype. For example, the WTRU may be configured with (e.g., three) TFTfilters and mapping rules for one or more, or each, of them (e.g. voicetraffic gets mapped to priority access group 1, video traffic topriority access group 2 and data traffic to priority access group 3).The WTRU may perform traffic inspection to determine the traffic classof one or more, or each packet, and/or it may look up the configuredmapping rules to determine which priority access group may be used, forexample.

The WTRU may determine the priority access group(s) to use based on amapping of EPS bearer and/or radio bearer from which a WTRU, perhapsacting as a relay and/or (e.g., first) receiving the data over acellular/Uu link, may receive the data, to the priority access groupover the D2D link. For example, a WTRU acting as a relay may beconfigured with separate EPS/radio bearers to transmit data fordifferent priority levels. The WTRU may map data received over aspecific EPS bearer to a specific priority access group, perhaps forexample based on pre-configured and/or signaled (e.g. by the eNB orProSe function) mapping.

The WTRU may determine the priority access group(s) based on a deviceconfiguration, on a per device basis (e.g. one or more or all servicesfrom that devices may use or always use the same or similar priorityaccess). The WTRU may be configured with a device/WTRU priority, forexample, based on hierarchy in the group (e.g., fireman chief isconfigured to have highest priority in the group). The WTRU maydetermine the priority access group(s) based on observed trafficcharacteristics in the WTRU. The WTRU may maintain past and/or ongoingtraffic characteristics (e.g. inter-arrival time, data rate, etc.)and/or may determine appropriate priority access group that may be usedto fulfil those traffic characteristics. The WTRU may determine thepriority access group(s) based on the function of the D2D WTRU. Forexample, if the WTRU may be operating as a relay, some or all trafficmay be mapped to a certain priority access group, or the WTRU may beconfigured to use different (e.g., higher) priority access groups whenoperating as a relay. The WTRU may determine the priority accessgroup(s) as a function of services configured by higher layers. Forexample, if higher layers request a D2D request for emergency service,the WTRU may determine the usefulness to use emergency priority accessgroup.

The configuration parameters described herein may be provided to theWTRU, for example, along with D2D service or bearer configuration, suchas by RRC or higher layer signaling (e.g. from the ProSe function). TheWTRU may be pre-configured with the mapping rules.

An in-coverage WTRU may be configured to report the priority accessgroups the WTRU may be using to the ProSe function/eNB. The eNB may begiven the configuration parameters described herein (e.g. mapping of LCGID, logical channels, priority level, and/or the priority access group)from the ProSe function and/or from another node in the network (e.g.MME), for example in scenarios such as where the mapping might not bedetermined (e.g., solely) by the WTRU, among other scenarios.

Selected priority access pools may be utilized for transmission.

The WTRU may determine how to multiplex the data into the selectedpriority access groups and/or transmit data using the characteristics ofthe priority access group. Features described herein may be applicablefor the case where the WTRU in one transport block can (e.g., only)multiplex data belonging to one source-destination pair and/orapplicable to the case where the WTRU can multiplex data belonging todifferent destinations.

The WTRU may determine how to multiplex and where to send some or alldata using one or more (e.g., only one) determined priority accessgroup. For example, the WTRU may determine to send all D2D using thepriority access group with highest priority among the selected accessgroups (e.g. if a D2D emergency service was requested by higher layers,some or all traffic from that device may be sent using emergencypriority access group). For example, the WTRU may determine the highestpriority service or priority access group that has data available anddetermine the resources or transmission characteristics in which thispriority service can be transmitted. The WTRU may be allowed tomultiplex priority services together (e.g., any of the priority servicestogether) and transmit them using the transmission characteristics ofthe highest priority data. Logical channel prioritization may beperformed in the transmitter, for example, to prioritize higher trafficclass from lower traffic class for one or more, or each, PDU creation.In a case where the WTRU is limited to multiplexing data from onesource-destination pair, the WTRU may determine the highest priorityservice or data across destination(s) (e.g., all destinations),determine the transmission characteristics and resources for thatpriority and may multiplex data from different priorities belonging tothat destination in the same PDU, e.g., according to LCP and availablespace.

The logical channels that can be multiplexed together may further berestricted to the destination in which the highest priority servicewithin that access group belongs to.

The data may be segregated to be sent using multiple priority accessgroups. For example, the WTRU may determine to multiplex data belongingto the same priority access group together and/or transmit them usingthe characteristics of the selected priority access group. If one ormore (e.g., two) priority access groups are configured (e.g., high andlow), the WTRU may classify the configured logical channels into one ormore (e.g., two) groups, and it may run (e.g., individual) logicalchannel prioritization to multiplex logical channels within one or more,or each, group into a separate packet.

One or more, or each, packet may be sent to lower layer, for example,along with a priority access group indicator. One or more, or each,packet may be associated with a separate indicator, for example, toindicate that pre-emption may be used to transmit the packet (e.g., ifsupported).

Triggers to determine priority access group may be described herein. TheWTRU may determine the usefulness to select priority access groupsand/or change priority access groups it may be using on detecting one ormore of the following triggers: upon initiation/termination of D2Dservice (e.g. emergency call); when D2D data may be available totransmit; when D2D data may be available to transmit, for example at thebeginning of a scheduling period; when the function of WTRU changes(e.g., WTRU may start and/or stop operating as a relay); when the newD2D resource configuration may be provided from the higher layers.

Priority access group may change. When the WTRU may select a newpriority access group and/or decide to remap D2D data to a differentpriority access group(s), the WTRU may be configured to perform one ormore of the following actions: stop using the earlier priority accessgroups for resource selection; determine traffic types and logicalchannels or group of logical channels that may belong to selectedpriority access groups; perform resource selection to select resourcesand/or transmission opportunities for one or more, or each, of selectedpriority access groups; perform logical channel prioritization for oneor more or all logical channels that may belong to a selected priorityaccess group and/or generate packet.

Although features and elements are described with reference to LTE(e.g., LTE-A) and LTE terminology, the features and elements describedherein may be application to other wired and wireless communicationprotocols, for example, HSPA, HSPA+, WCDMA, CDMA2000, GSM, WLAN, and/orthe like.

Although features and elements are described above in particularcombinations, one of ordinary skill in the art will appreciate that oneor more, or each, feature or element can be used alone or in anycombination with the other features and elements. In addition, themethods described herein may be implemented in a computer program,software, or firmware incorporated in a computer-readable medium forexecution by a computer or processor. Examples of computer-readablemedia include electronic signals (transmitted over wired or wirelessconnections) and computer-readable storage media. Examples ofcomputer-readable storage media include, but are not limited to, a readonly memory (ROM), a random access memory (RAM), a register, cachememory, semiconductor memory devices, magnetic media such as internalhard disks and removable disks, magneto-optical media, and optical mediasuch as CD-ROM disks, and digital versatile disks (DVDs). A processor inassociation with software may be used to implement a radio frequencytransceiver for use in a WTRU, WTRU, terminal, base station, RNC, or anyhost computer.

What is claimed is:
 1. A first wireless transmit/receive unit (WTRU)comprising: a processor configured to: transmit a first schedulingassignment for a first sidelink data transmission, the first schedulingassignment indicating a first priority level associated with the firstsidelink data transmission, a first duration associated with the firstsidelink data transmission, and one or more first resources; receive asecond scheduling assignment from a second WTRU for a second sidelinkdata transmission, the second scheduling assignment indicating a secondpriority level associated with the second sidelink data transmission, asecond duration associated with the second sidelink data transmission,and one or more second resources; determine that one or more firstresources being used by the first WTRU for the first sidelink datatransmission correspond with a second resource of the one or more secondresources; determine that the first priority level is less than thesecond priority level; select one or more third resources for the firstsidelink data transmission based on the determination that the one ormore first resources correspond with the second resource and thedetermination that the first priority level is less than the secondpriority level; transmit a third scheduling assignment; and transmit thefirst sidelink data transmission on the one or more third resources. 2.The first WTRU of claim 1, wherein each of the one or more firstresources indicates a resource selected by the first WTRU for the firstsidelink data transmission.
 3. The first WTRU of claim 1, wherein theprocessor is further configured to stop sending data on the one or morefirst resources upon expiration of the first duration indicated in thefirst scheduling assignment.
 4. The first WTRU of claim 1, wherein theprocessor is further configured to send a resource release indicationupon expiration of the first duration indicated in the first schedulingassignment.
 5. The first WTRU of claim 4, wherein the resource releaseindication indicates that the one or more first resources can bereleased.
 6. The first WTRU of claim 1, wherein the first durationcomprises a length associated with a scheduling period that the one ormore first resources are available for the first sidelink datatransmission.
 7. The first WTRU of claim 6, wherein different lengthsare used for different scheduling periods.
 8. The first WTRU of claim 1,wherein the processor is further configured to measure signal strengthassociated with the second scheduling assignment, and wherein theprocessor is further configured to exclude a resource from the one ormore second resources based on the measured signal strength beinggreater than a pre-defined threshold.
 9. The first WTRU of claim 1,wherein the first duration is equal to the second duration.
 10. Thefirst WTRU of claim 1, wherein the third scheduling assignment indicatesone or more third resources.
 11. A method performed by a first wirelesstransmit/receive unit (WTRU), the method comprising: transmitting afirst scheduling assignment for a first sidelink data transmission, thefirst scheduling assignment indicating a first priority level associatedwith the first sidelink data transmission, a first duration associatedwith the first sidelink data transmission, and one or more firstresources; receiving a second scheduling assignment from a second WTRUfor a second sidelink data transmission, the second schedulingassignment indicating a second priority level associated with the secondsidelink data transmission, a second duration associated with the secondsidelink data transmission, and one or more second resources;determining that one or more first resources being used by the firstWTRU for the first sidelink data transmission correspond with a secondresource of the one or more second resources; determining that the firstpriority level is less than the second priority level; selecting one ormore third resources for the first sidelink data transmission based onthe determination that the one or more first resources correspond withthe second resource and the determination that the first priority levelis less than the second priority level; transmitting a third schedulingassignment; and transmitting the first sidelink data transmission on theone or more third resources.
 12. The method of claim 11, wherein each ofthe one or more first resources indicates a resource selected by thefirst WTRU for the first sidelink data transmission.
 13. The method ofclaim 11, wherein the processor is further configured to stop sendingdata on the one or more first resources upon expiration of the firstduration indicated in the first scheduling assignment.
 14. The method ofclaim 11, wherein the processor is further configured to send a resourcerelease indication upon expiration of the first duration indicated inthe first scheduling assignment.
 15. The method of claim 14, wherein theresource release indication indicates that the one or more firstresources can be released.
 16. The method of claim 11, wherein the firstduration comprises a length associated with a scheduling period that theone or more first resources are available for the first sidelink datatransmission.
 17. The method of claim 16, wherein different lengths areused for different scheduling periods.
 18. The method of claim 11,further comprising measuring signal strength associated with the secondscheduling assignment, and wherein the processor is further configuredto exclude a resource from the one or more second resources based on themeasured signal strength being greater than a pre-defined threshold. 19.The method of claim 11, wherein the third scheduling assignmentindicates one or more third resources.
 20. A first wirelesstransmit/receive unit (WTRU) comprising: a processor configured to:transmit a first scheduling assignment for a first sidelink datatransmission, the first scheduling assignment indicating a firstpriority level associated with the first sidelink data transmission, afirst duration associated with the first sidelink data transmission, andone or more first resources; receive a second scheduling assignment froma second WTRU for a second sidelink data transmission, the secondscheduling assignment indicating a second priority level associated withthe second sidelink data transmission, a second duration associated withthe second sidelink data transmission, and one or more second resources;determine that one or more first resources being used by the first WTRUfor the first sidelink data transmission correspond with a secondresource of the one or more second resources; determine that the firstpriority level is less than the second priority level; select one ormore first resources or one or more third resources for the firstsidelink data transmission based on the determination that the one ormore first resources correspond with the second resource and thedetermination that the first priority level is less than the secondpriority level; transmit a third scheduling assignment; and transmit thefirst sidelink data transmission on the one or more first resources orthe one or more third resources.